Before it spawns, a purple portal-type object will appear.
His sprite is the same as that of the Imp Overlord, but with purple eyes.
He deals poison damage whenever it hits the player. The base poison damage is 1000.
His move set is very much different than that of the Imp Overlord. Imp Vanguard only has the basic attack to smash the player and teleport.
The Imp Vanguard can drop the Imp Overlord's Tentacle item, just not as commonly as the Imp Overlord does.