is actually a pretty devastating duelist.
This is mostly due to his ability to transform a 1vs1 into a 5vs1 and how strong his passive is with more ghouls out.
The passive reduces all incoming damage by 5% and increasing his auto-attack damage by 5% for each ghoul he has out. With all 4 ghouls out (the ulted champion counts as one) he pretty much has a
ult applied to him. The hosts then get 35% of his AD and health.
His Q is an auto-boost that once hit will summon a ghoul that also heavily boosts his movespeed.
The w is an instant ghouls with a constant slow effect keeping you in range.
His E is one of the best sustain abilities in game with how the ghoul heals him for every attack it does.
The Ult can summon a clone Yorick (or any teammate) that deals 75% of the targets auto-damage and can stay up for 10 seconds. If the target dies while the ult is still active though they are fully revived (full health) for 10 seconds.
By late game Yorick, while kinda crappy in teamfights if his ult is down, is actually really strong in duels and can duel most anyone by just ghoul spamming them to death. He becomes really tanky while dealing a lot of mixed damage.