Doom Prevails is the villain deck of the set, a Grixis (blue, black, red) build that leans into scheming, conniving, and slowly bleeding the table dry, exactly the kind of patient, plot twisting gameplan a comic book mastermind would draw up
Gishath is made up almost entirely of terrible, bulk rare dinosaurs and uncommons plus the same tribal stuff that is going to go up a little but do you want to be paying $20 for a card thats going to hit $23
The good news is that its definitely possible to get on board as people enter and leave the group all the time
Creatures you dont control get -1/-1 for each slime counter on them
Of course, you could always double up on combat damage triggers by having Yuriko, the Tiger's Shadow around
If both permanents are on the battlefield, both will trigger separately, allowing you to essentially double up on the effects that get triggered