His +1 ability is not really anything new - pay 1 life to draw a card is a pretty classic Black ability. Still, card draw is card draw, and it’s a +1, so it’s good. His -3 ability lets you destroy a creature. Considering that removal seems to be getting considerably slower in Standard, this could be an extremely relevant ability.
The ultimate ability creates an emblem for your opponent that is sort of Nekusar the Mindrazer on steroids. Forcing your opponent to lose 2 life for each card that is drawn by anyone at all is absolutely brutal. The question remains, though, how often will you reach this ultimate?
On the surface, this Ob Nixilis basically will draw you a couple of cards and destroy a creature for 5 mana. That seems acceptable. The ultimate is really nice and creates a very fast clock for your opponent, but it probably will rarely be attained. He seems Standard playable. It’s possible that he takes Elspeth, Sun’s Champion’s place in some Abzan lists, so there’s definitely room in the format for him.
In Commander, his emblem isn’t really so good in a multiplayer environment, unless you really want to pick on someone and kill them outright. In Duel Commander, I can see him being really good for picking off an opposing commander then getting a fast clock going for you to finish the game off. As black Planeswalkers go, Ob Nixilis of the Black Oath from Commander 2014 is a better option.
All in all, this Ob Nixilis won’t break any formats, but he’ll be super good in Limited, playable in Standard and fairly decent in two-player casual formats. He’s sort of underwhelming for multiplayer Commander and shouldn’t see any play in Eternal formats.