Sirene's Lane Gengar Gengar - Sirene
Build Path

Will-O-WispFirst Pick
Damage. Burn.

Hex
AOE damage, increased against poisoned targets.

Sludge Bomb

Phantom AmbushUNITE
Invisible. Movement Speed up. Then: AOE damage. Slow.
Razor Claw
After using a move, the Pokémon's next basic attack deals more damage. If held by a melee Pokémon, the basic attack also slows opposing Pokémon.
Stat Boosts
Guide
If you don't want to take Razor claw, take either Focus Band, Buddy Barrier or Score Shield.
Reason for Razor Claw is to help with farm secure - using lick to pull camps away from an enemy and then having a boosted auto empowered by razor claw lets you secure or even steal farm. It also gives you a bit more damage in these early engagements, which help you not be a pushover in lane.
Once you hit level 5 and get access to hex, you get boosted auto resets often, and Razor claw helps you take advantage of that. If you don't believe me, try this build for yourself. You might be surprised.
Cons: you are super squishy, with no buddy barrier and no access to focus band. You need to be aware of this. The way to play around this is to try and wait for an engagement to start and for enemies to use a few of their skills before you engage. It is harder for them to retaliate with attacks on cooldown. Prioritize killing their healers and carries first, if possible.
Pokemon Unite .GG thanks user Sirene for sharing this guide on how to play Gengar. Be sure to support your favorite creators by upvoting their builds, videos, and anything else they share you find useful. You can also check this user's page for more build guides.
There are indeed many ways to play Gengar in Pokemon Unite, and you can find more builds here, as well as detailed information about Gengar's moves and the items you can assign to it.
Perhaps you have a better build in mind? Try creating your own!
For more information on build guides, check out our detailed FAQ page to answer any more questions you may have.