It replaces all your zombies combat damage with milling, and whenever creature cards get milled, youre rewarded with more zombies
Interestingly, because Saheelis ability can be activated at instant speed, you can even copy Portal to Phyrexia during your opponents end step and double up on triggers during your upkeep
However, they do buy you a couple of turns before opponents make their big attack
Once you have a big enough storm count, typically around six, you can flip Ral into his planeswalker side, which then lets you activate Ral's final ability on the same turn, giving you access to a bunch more spells for free, until you find your copy of Grapeshot
Cost : This is a number in the top left corner of the card
Its an incredible deck that rewards timing and thinking through your turns in advance