For just one white mana, you get to permanently remove a creature from the game
You play a turn-two Cylian Elf
Those lists typically already go pretty wide with cheap, 2- to 3-cost creatures, and this would be a great top-end that solidifies your board and has a lot of potential to come out early
Selvala costs one generic and two Green mana to cost, and by paying one Green mana and tapping it you can add X mana in any combination of colors to your mana pool, where X is the greatest power among creatures you control
The combo is built around the non-green nephilim, Yore-Tiller Nephilim, Medomai the Ageless, and Viscera Seer (or any creature with a sacrifice a creature ability)
Not only does this card allow the ramp deck to find the necessary colors to cast Atraxa, Grand Unifier, but it also ramps you from four mana to six, setting up for an Atraxa the following turn