[RPG] Are there rules for dropping on an enethe as an attack

There are no specific rules for edge cases like this. In Pathfinder the GM is expected to rule in a way that makes sense.

I find in cases like this, combining what's obviously realistic with a check leveraging even tangential RAW that at least nominally makes some of it under the control of the character is good.

The way I'd rule off the cuff if this was presented at a table:

• A six second round combined with falling means no, you don't automatically get a full attack.
• Pathfinder has a Fly skill. Most people don't have it, but there is one. Make a Fly skill check - if you hit 10 you get one attack, and you get an additional attack for every 5 points over 10.
• This assumes it's a deliberate thing - like "jumping" instead of "falling" - if a monster did the teleport as a surprise this check would be 5 points harder.
• You can maybe sub in Acrobatics, but again at 5 points harder on the check.

Not "no," but not "you can do anything you want just because you asked" either.

The rules for falling do not address timing or actions at all. They only specify damage taken.

However, the general rules for the game are that things are atomic—you do one action, you do another, and you cannot mix them or interleave them. There are exceptions—Spring Attack, 5-foot-steps, etc.—but they are exceptional. Without some explicit exception, I would default to assuming that you must finish falling—more on what that means in a bit—before you can do something else.

Therefore, if, at any point in time, there is no longer ground beneath you, you fall immediately. You are not in control and cannot act normally. If it was your turn, that pauses until the fall completes—details still forthcoming—and it is effectively no longer your turn. This is similar to the situation with attacks of opportunity, which interrupt an action or turn to allow a different creature to act (and attack).

Some actions, principally immediate actions, can be taken out-of-turn and therefore always can occur during a fall. Feather fall is even specifically designed to be used just as you begin to fall. Likewise, if you have some relevant ability to act in the middle of movement—maybe Spring Attack if this was an intentional jump off a cliff perhaps—I would expect most DMs to allow it to apply, though the rules are murky about that. You could also presumably ready an action to take place after you’ve fallen a certain distance or when you’re a certain distance above the ground, but you would have to ready the action prior to falling in my estimation.

Dungeon Master’s Guide II specifies that on the first round of a fall from a very great height, a character falls at most 670 ft. So if you are higher than that, the fall “completes” for the turn, and you act after that.

Thereafter, each round is another 1,150 ft. Round-by-round durations in 3.5e are somewhat odd, but very clear: anything that is supposed to occur X rounds after some point, occurs X rounds later when you reach that same initiative count. Initiative does not change during a given turn, so your fall began on the relevant initiative count, and you continue to fall as soon as the initiative reaches that point again—that is, before any creature acts on that initiative count.

These numbers (670 ft and 1,150 ft) are a fair bit larger than dlras2 had calculated using the relevant real-world physics,¹ but then maybe the acceleration due to gravity is larger in D&D than on Earth.

There are no restrictions present in the rules on how you may spend your actions if your turn comes up in the middle of free-fall (that is, after dropping 670 ft in the first round, or after dropping 1,150 ft on any round thereafter). Presumably, if you only have a land-based movement speed, you would not be able to actually move, but you would get a move action, as well as swift and standard actions, as usual. Because of the abstractions present in the rules, this means that for shorter falls, if you fall during your own move action you can land and still make your Standard action afterwards. In theory, maybe some or all of that is actually going on during the fall but the game does not model that.

Personally, if this was any thing like a major part of a campaign I was running, I would houserule some way to move as a move action while in free fall—even without any kind of equipment you can aim yourself in a long fall, though I’d have to do some research on how much.

1. _{See the comments for dlras2’s calculation. Using real-world physics and a lot of estimation, and assuming you take 20d6 damage, i.e. 200 ft., to be the point at which you hit terminal velocity, you would move 470 ft. in the first round and 660 ft. per round thereafter.}