Ive heard some call it the green Shelly (Sheoldred, the Apocalypse) for formats like Standard and Modern and its not a perfect analog since Ouroboroid cant just solo people like Shelly can, and is worse against bolts but it does highlight something: letting this live for a turn or two can make life rough, even on its own
Sinistcha evolves from Poltchageist and has some incredibly useful abilities, like healing 30 damage from each of the player's Pokmon with its powerful "Matcha Splash" attack
Because it drains the life of every opponent as a free upkeep trigger, and converts that to scrying, you're always using it to set up your card draw
It could also find a way into GW counters decks that tap dorks, and Bant decks obviously
Nahiris Wrath deals damage equal to the total converted mana cost of the discarded cards to each of up to X target creatures and/or planeswalkers
A Landfall deck will definitely want to use Rampant GrowthRampant Growth, but an Artifact deck would benefit more from Mind StoneMind Stone