Is Skeleton Scavengers legal in Standard, Modern, and Commander?

Skeleton Scavengers is legal in: Legacy, Vintage, Commander.

What type of card is Skeleton Scavengers?

Skeleton Scavengers is a Creature — Skeleton. Its oracle text reads: "This creature enters with a +1/+1 counter on it. Pay {1} for each +1/+1 counter on this creature: Regenerate this creature. When it regenerates this way, put a +1/+1 counter on it."