Two demon-like, shape-shifting sisters who organise death duels between great warriors from any universes. They're, like, a crossover engine.
The Corvidae appeared in Gail Simone and Aaron Lopresti's Wonder Woman vs. Conan mini-series.
A team of five identical, supernatural killers with enhanced strength, poisonous elbow spikes, etc.
These guys appeared in the classic Mage: The Hero Discovered comics series, back in the halcyon days of a while ago.