Quote Originally Posted by Skrum View Post
Doesn't dim light give disadvantage, is that what you mean by -5?

Yes this would reduce the value of Skulker; my skill tricks for Medicine encroach on Healer too. But honestly, I don't care. I really don't like those kind of feats being in direct competition with "optimal" feat/ASI choices, and players feeling like they need to accept making themselves worse in order to get unusual or flavorful abilities.
Advantage/disadvantage on ability checks give a +/-5 modifier on passive ability checks. (PHB chapter 7 - passive checks) "If the character has advantage on the check, add 5. For disadvantage, subtract 5. The game refers to a passive check total as a score."

Quote Originally Posted by Skrum View Post
Maybe, but I'm trying to avoid massive blocks of rules text too. In the case of the "false position" one, I'm leery of stuff that implies that enemies will take a certain course of action. It just gets funky; how compelled are they to follow it? What actions would they take? It just gets annoyingly murky.
Why does it need to compel the enemy? They make choices and draw conclusions based on information that they have. If a player gives their enemy misinformation the enemy will take actions based on that misinformation and make mistakes.

The simplest example of this I can think of his tricking a dog you've thrown a ball. If you know what a dog does when you throw a ball you can get it to do that without even having a ball.

If you know that hobgoblins almost always go to investigate noises, you can make them go investigate an empty bush by throwing a rock into the bush.

If you know that during a fight, a hobgoblin goes to uncover a hidden rogue from their last known location, you can trick it into going into a trap or hazard or disadvantageous position by tricking it you are somewhere else. There's no compulsion needed, and no guarantees it will work.

This should work for both rational enemies as well as emotional enemies. If you can make a rational enemy make mistakes by manipulating its knowledge you should be able to an emotional enemy make mistakes by manipulating its emotions (through the charisma skills in that case).