Plots That Span Centuries Plots That Span Centuries can give you three schemes at once next turn, so your opponents are pretty much done for
While a 6/6 creature is not all that imposing, Deep Spawn has the ability to make itself untargetable until end of turn for just a single blue mana, effectively has some form of evasion with the Trample ability, and also mills cards from the top of your deck in to your graveyard during your upkeep (which can fuel further reanimation shenanigans on future turns)
As a mono black commander, supporting Sephiroth with plenty of disposable creatures or other cards that trigger removal allows you to gain card advantage, all while enabling a vampirism effect that helps you gain life while your opponents lose it
You can only use this effect of "Stream, Dragon Ruler of Droplets" once per turn
When I say this card has as many words as Animate Dead its often a question of basic complexity
It's strong from where I am sitting