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
Doomsday Confluence After Torment of Hailfire this is one of the coolest stuff to do in black with a lot of mana
Contents: 30 Tarkir: Dragonstorm Play Boosters
With that out of the way, lets look at the rest of Eris, Roar of the Storms abilities
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
as this card is already one that seems to be in plenty of decks at present, youll either want to get hold of multiple copies yourself, or find a way to counter it, and quickly