Doomsday Confluence After Torment of Hailfire this is one of the coolest stuff to do in black with a lot of mana
They require a small strategic action when first coming through the battlefield door and then they're yours forever, unlocking untold potential in the way we strategize and build
a 2/2 and four 1/1 creatures, or a 6/6 creature, or something in between, like a 4/4 that makes two 1/1 tokens
Like the three past dungeons, each initiative trigger will move a counter deeper along the Undercitys path and grant helpful boons - one room might dump some +1/+1 counters onto a creature while another lets someone scry the top two cards of their deck
With that out of the way, lets look at the rest of Eris, Roar of the Storms abilities
A staple for Kanto completionists