The cost of a new Liliana planeswalker is pretty high. But Vraska, Relic Seeker proved that six-mana planeswalkers have the right to live in Standard, if the power level is high enough.
Her ultimate ability is especially strong, as it removes lands as well, which is basically game-winning at that point. But she could be simply used for her card draw and sacrifice abilities alone, as those two pretty much control the game on their own.
So if you are looking for an extra planeswalker for your control deck, then look no further than Liliana, Dreadhorde General.