Short rests require an hour in which
a character does nothing more strenuous than eating, drinking, reading, and tending to wounds.
(PHB, page 186.)
Eldritch Master takes one minute, and doesn't specify what you can and can't be doing in that time. It's unclear (i.e. open to DM ruling) if you have to spend that minute doing nothing except entreating your patron, but even if that's true, sometimes, you don't have an hour. If you're running away from something, you might just be able to get a minute lead on it to quickly get your spells back. An hour lead is a lot less likely.
A minute is a very short time out of combat, and even in combat, it's 10 rounds. In a protracted fight you could probably pull this off. In a really protracted fight, you might need to. For example, if you're fighting the Tarrasque, your Eldritch Blast will be entirely useless. Once you're out of spell slots, you're going to be standing around doing nothing. (Slight exaggeration.) Your allies might be able to keep you alive for 10 rounds so that you can get some spells which have a chance of achieving something.
It shouldn't need pointing out, but an hour is 600 rounds, which is just not going to be possible in any combat. (Unless you're fighting a Dire Half-Dragon Fiendish Snail or something, but that's just getting silly.)
Of course, all of this is somewhat pointless if your DM is ok with you doing other things during the minute it takes to use this. For example, even if you're only allowed to use your movement, running around for a minute screaming at your patron for help seems completely achievable. If your DM rules that you can fight as normal during that minute, then this feature might actually be too powerful. Get into a fight with a tough enemy? Start praying to your patron. That gives you 10 rounds to use all your resources, at the end of which you just get them back immediately. Personally, I wouldn't be quite that lenient, but that's up to your DM.
I am not focusing on “how do I best spend my enormous wealth?” since that’s much too broad for a question here; I am instead focusing on your requirements.
Sadly, for that we have to begin with this fact:
Crafting “All the Things” cannot be done
First, crafting “All the Things” is off the table. There is no way to do so in Paizo-published content. Items that do not replicate spells can have their spell requirements waived with an increase in DC, so the wondrous items you mention are fine, but scrolls cannot benefit from this. To produce a scroll, you must have the spell, period.
To get as many spells as possible, you could try to use mystic theurge, but you won’t succeed; you’ll be very far behind on both classes, and eventually you’ll run out of mystic theurge levels to take. If you could convince your DM to let you take a 14-level mystic theurge, and you’re starting at 20, you’d hit most things – but would still lack any spells not on those lists (say, druid spells if your divine side is cleric).
The other thing you could conceivably do is use items to make items, but that’s hardly from scratch: the first item had to come from someone who had the spell, and that won’t be you. Besides that, it’s pretty much pointless; a wand of whatever could make fifty scrolls of whatever but all that accomplished is turning your charges into more fragile, more difficult-to-use scrolls, at considerable cost and taking considerable time.
There are no good analogues to vitriolic spear
The attack you mention is clearly the warlock’s eldritch blast modified by vitriolic blast and quite probably eldritch spear. There are no good options that mimic this attack.
First of all, at-will magic is something Paizo apparently detests; their one example of it, the kineticist from Occult Adventures, is insultingly weak, and moreover it isn’t actually at-will: its abilities deal self-damage, and the kineticist is extremely limited in how much of that damage (called burn) they are allowed to take. The damage cannot be healed except by resting, so that basically becomes a per-day limit (and a tight one). There is a very counter-intuitive way to play kineticists in which you only use your 0-burn abilities; that’s basically at-will, and it works better than most kineticists, but it is still pretty terrible.
Secondly, mundanes aren’t doing a lot better here. While 3.5 had, for example, the gloves of endless javelins and the like, there are no options in Pathfinder for infinite ammunition, even plain old mundane ammunition. So a longbow isn’t a great analogue here, even if you can carry a lot of arrows. Talk to your DM about whether or not he tracks those, though: many don’t, and that could sort of be an answer.
Firearms are actually somewhat closer, kind of, to eldritch blast – like eldritch blast, they are a touch attack (and also like eldritch blast, their damage is difficult to improve). Unfortunately, the ammunition problems for longbows are dramatically worse with firearms: powder and bullets are very expensive, even for gunslingers who see massive discounts. Furthermore, firearms break very easily, making them painfully unreliable.
Closer to truly-infinite ranged attacks is a returning thrown weapon. This will come back to your hand at the start of your next turn (you have to be where you were when you threw it to catch it), eliminating the ammunition issue. If you have multiple attacks (and at 20th you have at least two), you need multiple returning weapons, or (much cheaper/more flexible) a blinkback belt though the latter works poorly unless you have Quick Draw. Quick Draw is close to required for a thrower anyway, though, so the blinkback belt is definitely the better play.
However, even that falls far short of vitriolic spear: most thrown weapons have very low range, you have to catch it, and most importantly, you need to hit real AC, not touch AC. That makes such weapons dramatically less reliable than vitriolic spear. You’re going to need better BAB, and quite likely better Dexterity, than you had as a warlock if you want to hit as frequently, and you’re also probably going to need to invest in your weapon, with feats (Far Shot) and magic (distance) to improve the range.
You can do some warlock-like things with ranged attacks though
The eldritch archer archetype for the magus is finally a ranged version of the magus that doesn’t suck, and magus is a fairly solid class for you. (Note that eldritch archer is quite new, and the list of archetypes on the magus page on the SRD hasn’t be updated to include. It is, in fact, a real thing, from Heroes of the Streets, and I’ve linked it since it can be difficult to find.)
The advantage of the magus is Spell Combat and Spellstrike. The former allows spellcasting in the middle of a full-attack, and the latter allows touch spells to be delivered with weapon attacks. The eldritch archer changes these to allow Spell Combat to be used with a ranged weapon and without a hand free (at the cost of the ability to improve Concentration checks), and using ranged weapons to deliver ranged touch attacks.
This means that an eldritch archer can deliver spells alongside a weapon attack. This seems very similar to the way Eldritch Essences were applied to the warlock’s eldritch blast, and goes a long way towards making your mundane weapon attack magical again.
Furthermore, the eldritch archer adds that returning property to the list of things that can be applied to weapons with Arcane Pool, along with distance and nimble shot (and at the cost of dancing, keen, and vorpal as options). Those definitely help in mitigating the problems associated with weapons that you did not have with eldritch blast.
So I recommend the eldritch archer here. The magus spell list is not going to be stellar at scroll scribing, but nothing is going to emulate Imbue Item in Pathfinder anyway. You can still be fine at crafting wondrous items.
The arcanist, on the other hand, is a wildly imbalanced and broken class. Seriously, I cannot more strongly recommend against inflicting that on your group.
Constant flight
At-will fly is not the same as constant flight: the headband of aerial agility +6 requires a standard action every 8 minutes to re-up the fly spell. It is again worth asking your DM if he’s going to be tracking this: it’s a headache for player and DM both, so the DM may simply waive it in favor of constant flight.
If not, and you want true, constant flight, wings of flying are 54,000 gp; cheaper than the headband, but no bonus to Intelligence. The maneuverability is also only average, but this means much less in Pathfinder than it did in 3.5. Being winged flight rather than just gravity-defiance is also a drawback (you can be tripped), and of course 54,000 gp is still vastly too much, but it’s what you’ve got available.
At-will Tactical Teleportation
Get a wand of dimension door – while it will require replacement eventually, it is much cheaper than an at-will cape of the mountebank, and has the further advantage of being a spell that you cast (albeit through the wand) – which makes it compatible with Spell Combat. The cape of the mountebank doesn’t have that feature. Since you can actually just cast dimension door yourself, you also qualify for the Dimensional Agility feat; for once, that feat is probably worthwhile, so you can continue acting after using it.
Using the wand will basically require that you only use one hand to attack, but that’s OK for thrown weapons.
Also, you could take Craft Wand and make your wands of dimension door; you actually have that spell. It will take three weeks to produce one, and cost 10,500 gp each. Note that summoners get dimension door as a 3rd-level spell: their slower spellcasting progression means that it still requires caster level 7th, but a 3rd-level spell at caster level 7th is still ¾ the value of a 4th-level spell at caster level 7th: a summoner could produce the wand in 16 days for 7,875 gp (and you could buy it from an NPC summoner for 15,750 gp).
Blindsense
Blindsense isn’t really all that good, and most options for it are overpriced. The eyes of the dragon are, in fact, probably your best bet with that much wealth. Still overpriced, but you can afford it.
Skill points
Eldritch archer gets 2 + Int skill points, but is Intelligence-based so that helps. Ultimately, the 3.5 warlock also got 2 + Int skill points and wasn’t Intelligence-based, so this ends up being mostly the same, but sadly not better.
Alternative: seriously, try to port the warlock
This answer fails on a lot of levels to actually deliver on something warlock-like. I am actually surprised at just how frustrating it was to try to find better answers for you.
Paizo has an unreasonable position on at-will abilities, and is not likely to publish anything any time soon that will work well for the warlock. As mentioned, the kineticist is terrible. But Pathfinder changes little from 3.5, and the warlock would require very little modification to work in Pathfinder. Many, many people have done it; it’s not a problem. I strongly suggest that you do so, rather than trying to bastardize the character with something jury-rigged together from Paizo material.
Best Answer
An unseelie fey warlock: intense, compelling, mysterious. Ever-changing, always-dangerous. Some warlocks focus on eldritch blast and damage, and have little use for Charisma, but I don’t think that’s you—I imagine you’ll be taking few Eldritch Essences or Blast Shapes, and focusing a lot on invocations and other effects that increase the number of ways you can mess with your opponents.
Distinctly Fey Stuff
This is stuff that involves being a fey, or having fey heritage, or interacting with fey. The reasons these are appropriate should be obvious.
Racial Stuff
The unseelie fey template from Dragon vol. 304 is extremely potent for its minimal level adjustment. Probably unreasonably so, actually; many DMs will balk at it. Then again, the warlock class is on the weak end so maybe your DM will allow it.
Pixie warlocks are somewhat traditional: their permanent greater invisbility is much better than the walk unseen invocation (which is as the spell invisibility and therefore broken by offensive actions), and their racial flight saves you an invocation on fell flight. That said, LA +4 hurts, to the point that I don’t really consider the pixie playable.
Another good fey is the petal from Monster Manual III: they’re Tiny, which makes them damnably hard to hit, and eldritch blast doesn’t care what size you are. They also get Improved Initiative as a bonus feat, and large ability score bonuses. They are “LA +2 (cohort),” which is frequently taken to mean that they cannot be player characters but only cohorts (e.g. from Leadership). However, a quick check at least reveals no actual rules for that entry, and really there’s not really any good reasons why petals cannot be player characters. Many DMs allow it, if forum posts are anything to go by. Note that LA +2 is still very problematic in general; I probably wouldn't do it unless I was starting at 8th level (and therefore had access to the warlock’s walk unseen invocation).
For both the pixie and the petal, you’ll have to do a fair bit to darken the character since those are, by default, fairly innocuous and pleasant fey. The warlock class is pretty good at that. The dead walk and summon swarm would be great choices for that. They’re pretty good choices in any event.
There are only two LA +0 Fey-type races I can think of, however: the killoren of Races of the Wild and the dusklings of Magic of Incarnum. The killoren are very “protectors of nature”-y, which I don’t think fits, though they can get Smite, which works well with your Charisma focus. Dusklings, on the other hand, are pretty fitting (Small size, midnight-blue skin, somewhat crazed appearance), but the −2 Intelligence hurts you because you’re going to want skill points and you only have 2+Int skills. That said, if you do go that route, Magic of Incarnum actually has some really good invocations in it, though the best one (incarnum blast) doesn’t need any Essentia to do its thing (since the Daze effect is way more important than the bonus damage).
Feats
Nymph’s Kiss (Book of Exalted Deeds) is a great feat for anyone, and warlocks can put it to particularly good use with their in-class Use Magic Device. It grants +2 on all Charisma-based skill and ability checks, a bonus skill point per level, and fey treat you as fey for the purpose of Diplomacy and negotiation. Also, you get a faerie lover (who is good-aligned, which helps since non-good fey can get quite ... jealous). The bonus skill point is particularly important since you want good skills, especially social skills, and have only 2+Int skills from warlock.
The Faerie Mysteries Initiate feat from Dragon vol. 319 is ridiculously powerful, though less so for a warlock than it would be for, say, a wizard. One of the options (Passions) is the ability to use Intelligence instead of Constitution for determining your bonus HP. Note that this is another feat that grants you benefits for getting it on with a fey. The biggest reason you would take Faerie Mysteries Initiate is so you can dump Constitution safely, and be rewarded more for pumping Intelligence, which in turn lets you get the skill points you want to be the beguiling silver-tongued trickster you really ought to be. Though the warlock’s 2+Int skills will constantly make that difficult.
Wizards also ran a regular column on their site called Fey Features; Life in a Noble House is one of the better ones. Several feats:
As well as Un/Seelie Court Member/Noble Kelir, which are both pretty lame mechanically, but the flavor in the article may be useful for describing your character, even if you don’t take the feats (which I don’t recommend you do). The Fey Kelir Magics article may also give some good ideas along the same lines.
Other Unseelie-ish Stuff
These are options available to you, as a warlock, that I think will enhance your unseelie flavor. I’m focusing on the creepy and the changeable here: fey are capricious, after all.
Races
The only LA +0 races with bonuses to Charisma are hellbred (Fiendish Codex II) and spellscales (Races of the Dragon), both of which take penalties to Constitution, which hurts a lot. Better if you can do Faerie Mysteries Initiate, though. There is also the so-called “lesser” aasimar, which also gets +2 Wisdom and is frankly overpowered, and not very fey, particularly unseelie. Actually, none of these are, I’m just mentioning them because you do care quite a bit about Charisma.
Alternatively, the changeling race (Eberron Campaign Setting) is like a match made in heaven here. They’re master tricksters, with the natural ability to change their appearance at will, their very name comes from fey folklore (a changeling is a fey creature substituted for a human child and left to be raised by the human parents). You can also aim for the excellent chameleon prestige class (which I’ll describe below), since Able Learner requires human or doppelganger and changelings are half-human, half-doppelganger hybrids. Also consider dipping rogue; a changeling rogue has a lot going for it (see below).
Other Classes
Dread Witch
The dread witch prestige class would be pretty solid, but it’s impossible for the warlock to enter. See if your DM will allow you to enter using frightful blast.
Binder
You probably aren’t going for hellfire warlock (though you should consider it; there’s no reason why an unseelie fey cannot have deals with devils), but even without it, a single level of binder (Tome of Magic) works really nicely: it gives you abilities you can change frequently, which is appropriate for capricious fey, and Naberius in particular gives you stunning social abilities. And Naberius is excellent for hellfire, if you go that route.
Cleric
While we’re talking about dipping in other classes, cleric is never a bad choice, between Turn/Rebuke Undead, Domains, and a smattering of spells. Cloistered cleric would also be a great 1st level, since it has 6+Int skill points. Knowledge Domain can also be traded for Knowledge Devotion (Complete Champion), which is a great boost for eldritch blast. Cleric also opens up entry to eldritch disciple (Complete Mage). Warlocks are pretty good at counterspelling, and with a cleric dip you can take Divine Defiance (Fiendish Codex II) to counterspell as an immediate action. To me, a fey-themed warlock should be about twisting his enemies about more than just straight blasting them; hard to argue with that kind of action denial.
Changeling Rogue
If you are a changeling, taking your first level as rogue (before starting warlock or anything else) has a ton to recommend it with the racial substitution levels from Races of Eberron. First of all, 10+Int skill points. Which, at 1st level, is ×4—that’s huge. Second, Social Intuition is awesome. For the record, Sneak Attack does apply to eldritch blast. For a non-changeling, starting with rogue is less great, though still worthwhile. I’d probably favor cloistered cleric, though, even over the changeling rogue.
Chameleon
Finally, the chameleon prestige class (Races of Destiny or here) is awesome, and two levels of it serve a warlock very well. Again, I’m focusing on fey being capricious: chameleons can change their abilities every day, including a feat they can change every day that can be a different Extra Invocation as you need it. Particularly potent if you don’t take the dead walk so that you can use your floating feat to get it when you need it: you do not lose control of your undead if you change your Extra Invocation to something else after you use the dead walk to make them. That’s pretty cool and very appropriate, I think, for this character. Plus, if you get to warlock 12/chameleon 2 you can make any magic item in the game by swapping in the requisite Item Creation feat and using Imbue Item.
Invocation Choices
You want a lot of lesser invocations, I think. If you are not a fey that has its own flight and/or invisibility, fell flight and walk unseen are obvious choices. Frankly, they’re almost every warlock’s choices for lesser invocation. And I’ve already mentioned why I think the dead walk is great for you.
And then there’s charm. I can’t imagine more fey-appropriate invocation. And it’s really quite good, though [Mind-Affecting] and [Language-Dependant] are going to limit its applicability badly.
Summon swarm is one of the best low-level invocations, and fits an unseelie fey for obvious reasons: death, decay, but nature and magic. One of the few things warlocks are better at than their true-spellcaster cousins: their version of summon swarm ends as soon as they stop concentrating on it, which prevents friendly fire. Eventually, many warlocks will want to switch summon swarm for something else (beguiling influence or dark one’s own luck are common choices) since the damage and save DCs stop being relevant, though you may want to keep the ability for thematic reasons.
Other good low-level, appropriate choices could be baleful utterance (destruction, particularly of things like locks; seems fey to me), beguiling influence, dark one’s own luck, and see the unseen.
At the greater level, chilling tentacles and nightmares made real are excellent crowd-control that have a heavy “that which goes bump in the night” feel. Meanwhile, devil’s whispers, despite the name, could not possibly scream unseelie louder if it tried: as suggestion, except your target then must make another Will save at a −5 penalty or forget they did what you suggested. Seriously, the chaos you can create with that in the right situation is astonishing.
For dark invocations, dark foresight seems quite appropriate, given fey’s association with omens, while word of changing is at-will baleful polymorph, which shows up in... almost every myth the fey have ever made an appearance in?
You probably won’t focus on your eldritch blast as much; you certainly have and use it, but you’ll probably want more variety in your invocations than simply getting new attachments for your gun. That said, if you want some essences, frightful blast and noxious blast seem fitting and appropriate, not to mention they’re simply quite good. If you do focus on eldritch blast damage (hellfire warlock, say), vitriolic blast becomes basically required to make sure that damage gets through SR.
I’d also mention that Complete Arcane claims that the various “Sudden” metamagic feats work on invocations “because” they apply no spell level adjustment. RAW, this is dubious as anything—the actual wording of those feats offers nothing that would allow them to apply to spell-like abilities like invocations, and the lack of spell level adjustment is completely irrelevant to anything as far as the rules for metamagic feats are concerned, but, if you buy that line and allow metamagic without spell level adjustment to apply to invocations, I would mention the excellent Invisible Spell metamagic from Cityscape. An invisible eldritch glaive is one of my favorite mental images in all of D&D 3.5e.
Some Inspiration