Well... how does your suggestion differ from what was implemented in ADOM?

[edit] Oh, I see. Well, then there must be possibility for spells to miss even visible enemy? Like, quickling might be able to dodge fire bolt even in corridors, while something large like moloch would be hit with 100% prob.

Personally I dislike this idea.

In ADOM if you hit the enemy in melee they can hit you back just as well as they would when you're visible. You can also hit invisible beings and cast spells on them with ease as long as you figure out the square they are currently on. This feature would change that.

Uh, sorry for editing post for so long... Wasn't it difficult enough in ADOM? About fighting back - well, if somebody hit me from NW, I can just swing sword in that direction, hoping to hit it.

I think you cannot aim accurately at invisible beings - you just have to guess where they currently are. They don't "fill" the squares completely. Of course the defensive bonus could be inversely proportional to the size of the being but on the other hand I guess large beings should be easier to hit anyhow.

This wouldn't make the game more difficult since invisible beings are fairly rare and this would apply also to the PC. I also proposed some ways to detect invisible beings in other feature suggestion.

Hmm. OK, I agree with you - but I just somehow dislike idea about missing/failing spells.