Should Darkness have a scorpion when it's in element with Nightfall? I'm not completely opposed on this point, but it's something which has to be kept in mind
On the mechanic itself: reducing maxhp is dangerous. Currently there's a topic that's worried over how much a weapon could be abused with said mechanic, nevermind a creature ripe for being adrenaline'd. How do you implement it so that it isn't only going to be used for Nightfall+Fractal (which a base 1 maxhp reduction would press it towards)
A way to ward off Fractal is to give it some way to interact well with Deathstalker. The current listed mechanic of being based on total current poison works somewhat, but the problem is that poison counters can get up to 20 pretty easily & reducing maxhp by 20 per scorpion is too much