Below are the build(s) we are using with Gengar in Pokemon Unite. Please note that for the items below we upgraded them to level 20 to increase their effectiveness!
Curse of Death
Battle Item: Eject Button
Held Item 1: Float Stone
Held Item 2: Shell Bell
Held Item 3: Wise Glasses
Move 1: Sludge Bomb
Move 2: Hex
This build is what makes Gengar really nasty to go against. The first move is Sludge Bomb to damage enemies by inflicting poison on those that it hits. Pair that with Hex, which deals extra damage to enemies that have a status condition and resets the cooldown to quickly finish off foes. The items that go along with this build are the Float Stone, Shell Bell and Wise Glasses. The Float Stone coupled with Gengar’s levitate ability help it move around the map quickly to engage in fights to support its allies. Then the Shell Bell and Wise Glasses increase its special attack while the former also reduces the cooldown length on Gengar’s skills. Eject Button works well with this build to add some extra maneuverability to Gengar’s bag of tricks. This build really shines when working the jungle (middle lane) where you’ll level up quickly and be able to start racking up some kills.