Suggestions for a CR+ for this ability?

[BlueWitch]

What would be a Challenge Rating increase for a Creature who had Regeneration 1 but it's every 3 turns instead of every 1 turn?

Would CR +1 be suffice?

[RandomPeasant]

Honestly, +1 is overkill. Even at low levels, that level of regeneration is at most going to result in the creature coming back after the party "kills" it. I think that might be worth going from CR 1/2 to 1 or maybe even 1 to 2, but if you compare the CR 4 Minotaur to the CR 5 Troll, the latter is getting regeneration 15 times faster than what you're suggesting, and it has other advantages over the former (though to be fair it's not strictly better).

[Zanos]

+0.

This regeneration is never enough to make the creature actually stay up for longer, and just adds a small "puzzle" for how to actually kill it. If a first level party can't figure out how to set something on fire, they're hopeless anyway.

[RandomPeasant]

The puzzle isn't really how to kill it, it's that you need to kill it in some special way. In that respect, the fact that the regeneration is too slow to fire in combat arguably makes it more challenging. With a Troll or Hydra, you're going to see it healing while it's fighting you, so even without any prior knowledge you have reason to suspect you'll need special measures to take it down. But here what's likely to happen is that you kill the thing without it healing at all, so you have no reason to even bother making a fire or tossing a flask of acid on it.

[BlueWitch]

I see! Thanks for the input, fellas!

CR +0 does seem more fair. Because its really only a problem if they escape.