Once you have an infestation, Saproling Symbiosis can be utterly explosive, proving Shroofus is much more dangerous than he looks
The Planeswalker Lolth, Spider Queen gains a loyalty counter every time one of your creatures dies, with loyalty abilities that spend one life to draw a card (+0), spawn buffed-up Spider creature tokens (-3), and create an Emblem (appropriately at a loyalty cost of -8) that, if you did an opponent anywhere between one and seven combat damage in a turn, bumps that damage up to eight
at the moment, UW is a little below the competitive tier
They sacrifice a lot of their own potential just to say, hey, remember this thing? even if it has nothing to do with the plot
Adventure cards are instants and sorceries attached to permanents that exile themselves when you cast them