dnd-3.5eshield
The comments in this question seem to indicate that being a tower shield user is a very detrimental choice in character-building. Having been under the impression for a long time that tower sheilds were good, I'm perplexed, and would like some explanation.
What are the downsides of carrying a Tower Shield? And is there ever a reason to have one that mitigates these downsides?
The 1st-level Sor/Wiz spell Kelgore's fire bolt [conj/evoc] (PH2 116) specifically "conjures a small orb of rock and sheathes it in arcane energy." There's just no way to substitute a different orb of rock for the orb of rock that's conjured, in much the same way a javelin of lightning (DMG 226) (1,500 gp; 2 lbs.) can't be substituted for the "stroke of electrical energy" in the 3rd-level Sor/Wiz spell lightning bolt [evoc] (PH 248). The magic creates the effect.
However, house rules might have the "handful of ashes" that are the spell Kelgore's fire bolt's material component change the spell's effect if the ashes were, for example, from a golem manual (iron) (DMG 258) (35,000 gp; 5 lbs.) or an ingredient a wizard had planned to use to create a homunculus (MM 154).
To expand on the first question and its answer, here's
Being a caster in the earlier days of Dungeons and Dragons meant managing focus and material components. Although house rules often eliminated them, were they not eliminated they afforded the DM the opportunity to deny a caster his ability to cast some spells, forcing the caster to solve problems using different spells or even different means entirely (e.g. fleeing; grappling, overbearing, and pummeling; lateral thinking; role-playing; throwing daggers or darts).
Spoiler for an Over-30-year-old Adventure Module
That said, even the most famous old school railroading adventure module, Schick's A4: In the Dungeons of the Slave Lords (1980), before play begins, removes all PCs' possessions, not just magic-users' components and spellbooks. Don't worry! Magic-users and illusionists get some scrolls.
The Player's Handbook (1978) says that
Material components for spells are assumed to be kept in little pockets, stored in the folds and small pockets of the spell caster's garb. Of course, some material components are too bulky, and in these cases the materials must be accounted for carefully. Also, some materials are rare, and these must be found and acquired by the spell user. (40)
Thus, beyond explicitly being able to "add or delete entire spells" as he was given permission to do a mere paragraph earlier, the DM is further given tacit permission to restrict access to spells by making some obviously inexpensive material components rare (e.g. the "tiny ball composed of bat guano and sulphur" [sic] as the material component for the 3rd-level magic-user spell fireball (73); the "small magnetized iron bars attached to two small canine statuettes, one ivory and one ebony" as the material component for the 6th-level magic-user spell repulsion (86)). Material components were both bad jokes and campaign management mechanisms.
In the Player's Handbook (1989, 1996) material components are handled differently:
When material components are required, these are listed in the spell description. Spell components are expended as the spell is cast, unless otherwise noted. [...] For cases in which material components are expended at the end of the spell [...] premature destruction of the components ends the spell. (114)
And that's it. Without optional rules material components are flavor text. A caster has the material components with which to cast his spells unless the DM uses the the section titled Spell Components (Optional Rules):
If the spell components optional rule is used in your campaign, your wizard or priest must have these items to cast the spell. Without them, he is helpless, even if the spell is memorized. For simplicity of play, it is best to assume that any spellcaster with any sense has a supply of common items he is likely to need--wax, feathers, paint, sand, sticks, and fluff, for example. For expensive and rare items, it is perfectly proper for your DM to insist that special effort be made to obtain these items. After all, you simply can't assume your character has a valuable pearl handy whenever he needs one! (113)
But the inclusion of the spell component pouch (5 gp; 3 lbs.) (PH 108, 111) in the Player's Handbook (2000) removed (except via rule O) the DM's ability to control what he considered problematic spells via making obviously inexpensive foci and components rare. Every wizard with a spell component pouch has within a "tiny ball of bat guano and sulfur" to cast the spell fireball (203-4) and a "pair of small iron bars attached to two small canine statuettes, one black and one white" to cast the spell repulsion (245)2 in addition to nigh infinite edible live spiders, miniature cloaks, powdered herring scales, undead creature bones, will-o'-wisp essence, and other gooey, icky, stinky stuff that must make anyone who carries a spell component pouch smell like a grease fire in crap factory.
War Story
The 1st-level magic-user spell identify (Player's Handbook (1978) 66-7) not only reduces the caster's Constitution score by 8 (knocking him unconscious for 24 hours if his score's reduced below 3) and only provides vague indications of what the magic item does if the caster first succeeds on d% (15% +5% per caster level) then successfully makes a saving throw versus magic, but also the spell identify has as its material components
- a 100 gp pearl,
- an owl feather,
- wine, and
- a live miniature carp.
Making sure goldfish survive while exploring a dungeon is difficult but necessary, as when a new magic item is found the "item to be identified must be examined by the magic-user within 1 hour per level of experience of the examiner after it has been discovered, or all readable impressions will have been blended into those of the characters who have possessed it since."
The 1st-level wizard spell identify (Player's Handbook (1989, 1996) 175) changed many of spell's details, but perhaps the most important change for anyone who labored under a DM who didn't house rule away material components was that the new edition removed from the list of identify's material components the live miniature carp.
Also of Interest
1 The material component for the spell grease [conj] (PH 237) is a "bit of pork rind or butter," and the material component for the spell silent image et. al. [illus] (PH 279) is a "bit of fleece."
2 "...the whole array worth 50 gp" was added in the 2003 Player's Handbook 3.5 (272).
For me this is largely about expectations, signposting and player agency.
The first point is expectations. How much was the tone of the campaign discussed before you started? Did you make sure the players were aware you were going for a world where their actions can have negative consequences and that you would follow through on these? This might sound silly, as I'm sure for a lot of people what I've just described is where the fun of roleplaying is, but you'd be suprised how many players have the expectation that they are never going to fail.
Then there are signposting, opportunies to spot the bad stuff and if it happens then do something about it. If I were a player and the only warning I got that something really bad was going to happen was right at the beginning of an adventure 3 months ago, then I think I would be entitled to be a bit frustrated. People have short memories and cannot be expected to be able to identify the important bits of information in everything you tell them as GM, let alone remember it for weeks/months at a time.
Lets take your first point as an example. Have they been made aware that the Kobolds renege on deals and have a reputation for not giving gold? When was this and by whom? Was it someone they had a reason to trust? If their only warning was a brief encounter with a minor NPC 10 weeks ago then you might want to think about reinforcing this somehow.
Assuming that you've given them plenty of warning and they still end up with no gold, the most important thing is to ensure that you provide a way of getting revenge and/or recompense. I know if I'd been doing a load of dangerous work and didn't get the gold I was promised that I would want to do something about it. The most important thing here is to give players the opportunity to act in revenge/response to whatever has happened to them. Maintaining player agency when something bad has happened to their characters is key in ensuring they don't feel hard done by or upset. There is nothing quite so bad as effectively being told 'Haha! You don't get any of the money you were promised and there's nothing you can do about it!'
Best Answer
Tower shields are not always bad. I've seen them used without being a hindrance (by someone who made a build around never having to make attack rolls). They're usually bad, though.
It's Bulky
For one thing, it weighs 45 pounds. Not a problem for a 20 STR character, but it can by itself cause encumbrance for a weaker character.
It's armor check penalty is a staggering −10. The question you mentioned had someone using it while hiding. −10 on a Hide check is nothing to sneeze at. Also applies to useful things like Tumble.
This still applies even if the shield is animated.
Attack Roll Penalty
You take a −2 to attack rolls while using it. Not a lot else needs to be said, as this just plain sucks. This applies even if the shield is animated.
Cover
You can use it to get total cover against ranged attacks. Great! Except if you do that, you:
That's pretty limiting for not a lot of defense.
Few classes have Proficiency
The list of classes that get proficiency with tower shields is very small compared to standard shields. Burning a feat for the tower shield is never worth it, and one penalty for using one without proficiency is that −10 armor check penalty applied to attack rolls. You really don't want that if you ever plan on hitting anything.
Are They Always Bad?
Not necessarily. If you're casting spells that don't require an attack roll, there's significantly less downside. There are a few builds that can make use out of it in some way, but if you're a melee combatant you probably don't want that −2 to attack under any circumstance.