Rules Compendium p. 150 (emphasis mine):
A reach weapon is a melee weapon that allows its wielder to strike at
targets that aren’t adjacent. Most reach weapons double the wielder’s
natural reach, allowing the wielder to attack at that reach but not
within its normal reach. A typical Small or Medium wielder of such a
weapon can attack a creature 10 feet away, but not a creature in an
adjacent square. A Large wielder wielding a reach weapon of the
appropriate size can attack a creature 15 or 20 feet away, but not
adjacent creatures or creatures up to 10 feet away. Tiny or smaller
creatures gain no advantage from reach weapons.
Rules Compendium p. 151:
A wielder gains no reach from a reach weapon that is too small. No
additional reach is granted by a reach weapon that is too big.
Based on those two things, we can answer your two questions:
- No. Tiny creatures threaten no squares around them, and reach weapons don't benefit them. As a larger reach weapon doesn't convey any extra bonus, they don't get any reach no matter how big the weapon is. (Though the mental picture of a tiny creature using a gargantuan halberd is pretty funny.)
- If the weapon is inappropriately small, they do not gain a reach boost at all. If it's inappropriately large, they do not gain an extra reach boost, but they would gain the normal reach boost for a creature of their size using a reach weapon. So a Dwarf using a large spiked chain gets the same reach as a Dwarf using a medium spiked chain.
I think your proposed feat is going to work as you intend. A fine spiked chain won't convey any reach, it'd just be like using a melee range weapon only doing a lot less damage.
Specific Q/A
Basic Question: Does a grig (MM 235) wielding a Tiny longspear (PH 116, 119) (2 gp 5 sp; 0.9 lbs.) threaten no squares, adjacent squares,
or squares 10 ft. away?
The grig is tiny, using a reach weapon. It therefore threatens no squares.
Then: What about a grig wielding two-handed a Small spinning sword* (Secrets of Sarlona 137-8) (50 gp; 3 lbs.)?
Threatens no squares. The spinning sword definition says that it's a reach weapon, and tiny creatures do not gain reach from reach weapons.
Then: What about a human wielding as a light weapon a Tiny longspear?
Threatens his natural reach only. Undersized reach weapons convey no reach, but they don't take away your natural reach (since said human could just punch that square).
Then: What about a human wielding two-handed a Large spinning sword (100 gp; 6 lbs.)?
Yes, the human would threaten squares 10' away, and 5' away (as the spinning sword works at close range, like a spiked chain).
Does The Rules Compendium Contradict The SRD/DMG?
No, it doesn't. The SRD's reach definition is as follows (emphasis mine):
Glaives, guisarmes, lances, longspears, ranseurs, spiked chains, and
whips are reach weapons. A reach weapon is a melee weapon that allows
its wielder to strike at targets that aren’t adjacent to him or her.
Most reach weapons double the wielder’s natural reach, meaning that a
typical Small or Medium wielder of such a weapon can attack a creature
10 feet away, but not a creature in an adjacent square. A typical
Large character wielding a reach weapon of the appropriate size can
attack a creature 15 or 20 feet away, but not adjacent creatures or
creatures up to 10 feet away.
Tiny creatures have a natural reach of 0. If you double 0, you get 0. Thus while the RC definition is lengthier, it doesn't contract what the SRD or DMG say.
The only thing in the SRD about oversize/undersize reach weapons is the bit in the above quote about using a reach weapon of the appropriate size. The RC expands on this, but again doesn't contradict what is said. (You could argue that in the SRD, an oversize reach weapon also doesn't grant reach as it's not "appropriate", but they didn't really spell out what they meant so I don't find the RC version problematic.)
Can A Tiny Creature Ever Get Reach?
Yes, as the DMG mentions:
Tiny, Diminutive, and Fine creatures have no natural reach. They must
enter an opponent’s square (and thus be subject to an attack of
opportunity) in order to attack that opponent in melee unless they are
armed with weapons that give them at least 5 feet of reach
That makes it clear that tiny creatures are not forbidden from getting reach, if they have some way to get it. Some examples of ways to do that:
- Shadowstrike (MIC) - On a weapon, activated to give that weapon +5' to it's reach. As it's just a flat addition to reach, it works even if the creature has 0' reach normally.
- Lunging Strike (PHBII) - Feat that allows you to make an attack with +5' to it's reach. Again this is a straight addition, so it works even if you had 0' reach.
- Inhuman Reach (LoM) - Feat that increases your character's natural reach by +5'.
What About Whips?
Whips have a different wording than the other standard reach weapons, as shown here:
The whip is treated as a melee weapon with 15-foot reach, though you
don’t threaten the area into which you can make an attack. In
addition, unlike most other weapons with reach, you can use it against
foes anywhere within your reach (including adjacent foes).
Compare to the Spiked Chain (another reach weapon that works in melee range):
A spiked chain has reach, so you can strike opponents 10 feet away
with it. In addition, unlike most other weapons with reach, it can be
used against an adjacent foe.
The "X has reach" wording on the chain is the same as you see for every reach weapon in the SRD, except the Whip. The first part of my answer covered how those work with larger and smaller creatures. But is a whip special?
- The strictest possible reading says that a whip is treated as a melee weapon. It also happens to have a 15' reach, and that number is specific. Does it change for larger or smaller creatures? The rules don't say. If you wanted to do a very strict reading, it's always 15', no matter the creature size. This starts to make no sense with gargantuan or larger creatures as it actually lowers their natural reach, and would give tiny creatures 15' reach with a whip and 0' reach with any other weapon, so it doesn't work very well at the table.
- A less-strict reading would instead say that a whip is a reach weapon (that can also strike in melee, like a spiked chain) that adds triple to the natural reach, instead of double for normal reach weapons. That means a whip scales up for larger creatures like other reach weapons do (except farther), and tiny creatures get no reach at all when using one. This has the virtue of being consistent with how reach weapons normally work. Also working in the favor of this one is that the reach weapon definition mentions whips as a reach weapon.
So for whips, it comes down to how much stock you put into the odd wording compared to other weapons. I can't give a reference for what the writers actually intended to do there, as one doesn't seem to exist. I do know that the second option is far more consistent in how it plays, so I would certainly favor it in actual play.
Best Answer
Although this question already has an answer, and rightfully so. I believe that anyone who visits this page with the same question should know the ups and downs of wielding over-sized weapons before coming to a conclusion.
Lets start with the Core Rulebook
A medium creature can use a large one-handed weapon as a two-handed weapon. Because you cannot increase a two-handed weapon, this means that a medium creature cannot wield a large two-handed weapon.
A medium short-sword is a light weapon on a Medium creature, and a one-handed on a small creature. Both creatures would utilize its 1d6 damage in this way, except the small creature takes a -2 penalty because of the size difference (when they could simply wield a longsword for the 1d6). A shortsword becomes a longsword, just as a longsword becomes a greatsword, as you increase size categories. The only difference is that you can take a -2 penalty to wield a smaller version of the weapon made for the next size category higher, at the same damage modifier.
Why would you wield a weapon of a size category not of your own?
1) You are a dual wielder (lets say a bard for example) and in your main hand you hold a longsword, and in your offhand you wield a whip. According to the equipment section, a whip is treated as a one-handed weapon, which means that in order to dual wield (assuming you have the two-weapon fighting feat) you will be taking a -4, -4 penalty. Wielding a "small" whip will treat the weapon as a "light one-handed" at the cost of a -2 penalty. This makes your two-weapon fighting penalties drop to a -2/-2 but increases your whip (offhand attack) by 2 because it is sized differently. Making your end result -2/-4 (essentially you are increasing the chance to hit with your main hand)
2) You have specific feats in weapon specialization and weapon focus, that give you a bonus to damage and hit with a specific type of weapon. Lets say my focus is longswords. Rather than wielding a short sword, it would be more beneficial to me to wield a small longsword because the -2 penalty to size is more than made up for with feats that give +2 to hit and damage when I use a longsword. This is linked in with the first reason.
3) You are playing a class that allows you to bypass the size restriction. For example: The barbarian archetype Titan Mauler. The Titan Mauler does not specifically say that you can wield weapons larger than yourself outside of the archetype description, though it is assumed through her abilities with the minor exception of Jotungrip: A titan mauler may wield a two-handed weapon in one hand though this weapon must be appropriately sized for her. Her level 3 ability allows her to reduce the "over sized" penalty by 1, meaning that for wielding a weapon that is larger than yourself you would take a -1 penalty instead of the -2. You would have to talk to your dm about this first to clarify.
How significant is the attack penalty compared to the damage?
A -2 is a difference of 10% on your hit chance. If you have +1 to hit at level 1, and you are versing someone with 12 ac. All you need to do is roll an 11 or higher to hit. Because there are 20 sides to the dice, each side represents a 5% chance, thus you have a 50% chance of hitting your opponent. If you take a -2 penalty, that would require you to roll a 13 to hit, thus making your chances of hitting a 40%.
Mathematically you can multiply your hit percentage by your average damage output to determine which is most optimal to use. In almost every situation, especially early on, the ability to hit your opponent is far better than the potential damage you could have done. As mentioned above, one of the major reasons to wielding an inappropriately sized weapon is to reduce your penalties to hit.
However there is more to take into consideration. As you level, your class will gain BAB (Base Attack Bonus). This bonus gets applied to your hit chance as well as attack bonuses from Feats, Equipment, Ability Modifiers, and Buffs. Your AC on the other hand, does not scale with your level, it instead only increases through Equipment, Buffs, Feats, and Relevant Ability Modifiers. It is because of this, that as you level you will begin hitting your opponents more and more. Your opponents AC will increase for the exact same reason that your attack bonus will increase -> You will have better equipment, and more feats / buffs at your disposal.
As a rule of thumb, do not invest in AC unless you can keep it roughly 20 + your level, (This does not apply right off the bat) example: Level 10 -> 30ac, Level 14 -> 34ac. Else your opponents will be hitting you so much, that it pays off more to simply have higher HP. This is because the attack bonuses at these levels is so high (from both Players and NPCs) that you will be getting hit anyway.
What exactly are the damage numbers?
On page 145 of the Core Rule Book is the chart for damage for weapons of larger or smaller size categories. This chart covers what is not mentioned in the equipment section -> The equipment tables only show the weapons medium and small damage, thus this chart shows it for Tiny and Large.
Each weapon has a BDR (Base Damage Rating), this number is not shown in the book and it is an average of the weapons potential damage. You simply take the lowest roll, and the highest roll and average the two: 1d6 ~ 1+6 = 7, 7/2 = 3.5. A 6 sided die will give you a BDR of 3.5. A greatsword is 2d6, thus 2+12 = 14, 14/2 = 7 (or simply put 3.5 + 3.5). If we were using a Dwarven Waraxe: 1d10, a large version would be 2d8 -> 5.5 increased to a 9.0. So when we say that you are increasing the damage by roughly 3, we are saying that you are increasing your average damage.
Simple so far? That is only the first step, we covered what the average damage potential was, but now I will talk about consistency. When a barbarian has a choice between a greatsword and a greataxe which one do they pick? When we look at BDR the GS is a 7, the GA is a 6.5. This is because both have the potential of reaching 12, but the GS will never do 1 damage. When you graph out all of the possible rolls on a dice, you notice that the more dice you roll, the more and more the outcomes are consistent and average. Rolling 2d6 has the highest percent chance of totaling a 7 than any other number, the next highest percent roll is either a 6 or an 8. When you roll multiple dice, you create a curve, and you make your numbers more consistent. With a single dice your numbers are much more random.
The third step is considering the damage range. As levels progress your opponents AC will not be the only thing you must overcome. You also have to take into consideration damage reduction. If your opponent has DR 10 silver, and you do not have any silver weapons. You are relying on your melee classes doing more than 10 damage. In this case you may hit your opponent 20 times, but if you cannot roll above a 10 on your damage, then your hit was for nothing. In the example of wielding a Large Greatsword (3d6 = 10.5 BDR) in comparison to a Medium Greatsword (2d6 = 7 BDR) taking a small penalty to hit to increase your BDR from a 7 to a 10.5 is extremely worth it!
Food for Thought: If you are versing an opponent that has DR 9 for example (Though this is rarely a case) you will have a higher percent chance of bypassing his DR with the GA than you will will the GS.
I realize the significance of attack bonus, but when should I sacrifice this?
1) When you are versing an opponent that has High DR
2) When you are versing a caster opponent, and the damage you deal applies to your opponents concentration check
3) When you are versing an opponent you believe to have less AC than the average and higher HP
4) When you have reached the point where your attack bonus is so high, that you will gladly take the extra damage (This typically happens after level 10)
My final words
I realize that this post may spark a lot of attention and negative approval. There was a huge argument about this and I believe that both sides of the argument should be presented. Yes a -2 penalty is significant, yet it is the exact same penalty that a dual wielder takes with both the two-weapon feat and a light offhand weapon. There are far more ways of increasing your attack bonus than there are your damage output. Thank you for taking the time to read this.