IF YOU'RE ONE OF MY PLAYERS, PLEASE STOP READING NOW! 
I'm currently running an online campaign that's a slight fork from the stock FS2 setting (more like 'Rivers of London as directed by John Woo'), and in the current adventure, the Magic Cop character, in his last investigation before his resignation takes effect, is finding traces of the demonic creature he faced earlier in his career, which got him recruited to the Magic Cop division of the Met. When first enoountered, he took a poisoned wound from the creature which laid him up in hospital for some time, near to death. Of course, by now he's a hero, and therefore going to be more resilient, but I still want to add a Foe Schtick to the creature (a Featured Foe, for reasons) that will give it that kind of fear. The main threat of the creature during the fight is just getting mauled, but the venom on the claws is there as a late surprise.
I was considering a version of the Contagion schtick (1 Impairment and treatment needed after), but I thought about the following instead, as the venom doesn't take effect until after the fight, and I don't want affected characters to miss the next parts of the timeline (unless they're dead, in which case, very sad, last words, flashbacks, next hero please) ...
Near-Lethal Neurotoxin: If a hero takes 1+ Wound Points from the creature during the fight, then at the end of the fight make a Constitution check or take 22 damage (reduced by Toughness). The difficulty of the Constitution check is 11 if damage was only taken in 1 sequence, 12 if in 2 sequences, and 13 if in 3 or more sequences.
The level of damage is inspired by the Radiation Poisoning foe schtick and the 'Extremely Toxic Poison' damage from p.109, as the relevant hero has been talking up how dangerous this thing is for ages - and as long as they don't burn all their Fortune in the fight, that should help with the Constitution check, if any of them don't Fortune Dodge their way out of harms way consistently (as they have a tendency to do).
(In the initial encounter with these, the heroes (four, with several advances) will face two of these, supported by demonic mooks of my own devising and a bunch of mortal threats.)
Any other suggestions, or any implementations of a similar power that would also work?