Ghoul's Blood poison: On hit radiates the target. On crit, target is slowed to a walk for 5 seconds or whatever.
Not sure if it's possible to implement temporary cripples or cripples or anything else.
I do not like the radiation part, it's only good to troll, no real effect on player in a fight. The slow walk should be for numbness, check below.
It is possible to implement temporary crippling. The hard part is to implement them, so that they work both on RT and Tb with the same result, as you Turn Based timer is 30 seconds, it would have not much effect, unless it lasts longer, but in that case it is too OP in RT mode.
Numbness poison: slight damage increase, on crit random arm crippled for a few moments.
Hm, how about reduced stats instead, like agility/strenght (less AP/AP regen) for some duration, or strength, reducing chance to hit (weapon min str. req.) and possibly disabling run if you got a lot of loot on you.
Crit effect could have a higher stat reduce, consecutive numbness poison hits, would refresh the duration.
Also, since we talk about poison, the effect should not be triggered immediately, but after some time. To cripple, use aim shot.