This little guy can be a hassle if you're trying to solo this task. Unless you're one of those snare and FD types. Just stand well back from his spawn point, snare, run him a little distance away, then FD and wait. Shadowloper will stay put because he's snared, and the ghouls will reset back to the spawn point (and subsequently despawn, though I'm not sure on the time frame. I didn't stick around to time them) and you can neatly pull the little gobby away to meet his messy fate.

Garish Festival Charm