Goodman Games

I'm making up a NPC that is a type II demon and has ESP. I'm having trouble figuring out a good way to work this mechanic with the players so that they don't always know their mind is being read (I don't want to be always asking players, "What is your character thinking right now?") Moreover, should I treat the ability like the 2nd level wizard spell or have it always being successful, with no save, etc.? How do you all handle this? Thanks in advance...

easiest, in my opinion, is to have it work like the spell of the same name.

However, the way I have handled monsters with ESP in the past is to simply be a bit "lazy" and "cheesey" about it: the ESP doesn't matter at all and isn't brought up... until the party is about to do something the creature doesn't like (lie to him, attack him, etc.) and then their ESP grants them the ability to respond to the player's declared action before it actually happens - the monster attacks preemptively or makes the soon-to-be-incoming attack invalid, and the monster just simply knows you aren't being honest.

...additionally, any 'plans' the group may have discussed prior to crossing paths with the demon -- stuff they have in mind but haven't acted on yet, or not acted on fully -- the demon could see in their thoughts. You heard it as a GM while the players discussed whatever it is; the demon can see it in the characters. These then would be the things the demon could 'prep for', i.e., get minions in the party's path, etc. Or that he/she could just call them out on, before the players get the plan in motion...

Also, anything in their history could be fair game, too.

Thanks a lot for the replies, you two. They are very helpful.

I think that the answer will come up in-game. Play the monster knowing he has this power, and you'll end up indeed playing along with it, undoubtedly.

Thanks Sky. Time will tell.