Can block bullets. When a bullet is blocked, he spits out 1-2 heart attack flies.
Synergizes with the following (most inherently, some hardcoded):
Extension Cord: Creates an electric laser between you and Lil Duke every couple seconds (inherent)
Duct Tape: Locks Lil Duke in place (inherent)
Sacrificial Altar: Lil Duke can be selected as a familiar to be sacrificed (mostly inherent, tracked via ItemConfig, see EntityPlayer:CheckFamiliar() if curious)
Box of Friends: Properly copies on use and vanishes in next room (mostly inherent, tracked via CollectibleEffects, also see CheckFamiliar())
BFFs: Flies spawned will be 1.2 times the size and deal double damage. Does not stack with Hive Mind. (hardcoded)
Monster Manual: Can be selected from the pool of random familiars (mostly inherent, same deal as Box of Friends)
The Twins: Chance of being duplicated on new room (mostly inherent, same deal as Box of Friends)
Orbiting familiar, deals no contact damage.
Can block bullets. When a bullet is blocked, he spits out 1-2 heart attack flies.
Synergizes with the following (most inherently, some hardcoded):