Anything you can think of—the catalyst depends on what you're looking to summon. It might be a sacrifice, or it might be an object that once belonged to the summoned being, or it might be something that's associated with the being.
If there isn't a catalyst, then the summoner might be used as one. Hence—if there wasn't a catalyst, then the conduit might have affected the summoning . . .
It's also possible that any catalyst here is already contaminated—nothing we have here wasn't in some way touched by Hell, including ourselves.
no subject
If there isn't a catalyst, then the summoner might be used as one. Hence—if there wasn't a catalyst, then the conduit might have affected the summoning . . .
It's also possible that any catalyst here is already contaminated—nothing we have here wasn't in some way touched by Hell, including ourselves.