Cori Mountain Monastery Land This land enters tapped unless you control a Plains or an Island
Valakut Awakening / Valakut Stoneforge Valakut Awakening sees a lot of play in EDH combo decks as a filter card selection piece that allows you to fix bad hands or to get rid of some redundancy you might have
Rampaging Ferocidon stops lifegain and punishes creature plays, especially go-wide strategies
In a blog, Mark Rosewater, lead designer on the game, said that it is counter-intuitive to have the Ring bring in-game positive effects, but it was the only way to get players to actually interact with it
In December Tomer from MTG Goldfish put up a YouTube video addressing the question: In the video, he reached out to Frank Karsten for some more statistical help to evaluate that question
Mechanics like delirium, delve, and threshold are very good in Sultai decks, so be on the lookout for those