This typically means mana-acceleration effects that will help you produce eleven mana naturally for someone like Ulamog, the Infinite Gyre when you can't bring him to class for Show and Tell
Firebending is the most elegant
Something like Charred Foyer // Warped Space may not be at its best in this deck (as much as I want to, I wont talk about how well thisd fit in a Prosper, Tome-Bound EDH deck), but if you manage to unlock both doors, you essentially have a nice engine that works by itself
And, of course, I always want someone twitchy when they think about attacking me
Ulvenwald Oddity / Ulvenwald Behemoth Ulvenwald Oddity is the perfect addition to the mono-green stompy deck
Trance ability allows her to mill two cards at the beginning of the combat phase in order to gain flying, which means she can't be attacked except by other creatures with flying