The fact that you can instantly use Sorin's ultimate ability makes him one of the most valuable new planeswalkers in Core Set 2020.
Just imagine that on Turn 3 you can play such overpowered vampires like Champion of Dusk and The Haunt of Hightower. Both of those cards can be game-winning when played so early in the matchup.
It's also nice that players can easily repeat this action by using the first two abilities that both uptick the loyalty counters.
With such low cost and huge possibilities, Sorin can easily become the best black planeswalker in the current meta.