Etali, Dinosaur Rider

This spell costs {2} less to cast for each dinosaur
you control.
Flying, double strike, vigilance, trample, indestructible
Whenever Etali, Dinosaur Rider attacks, exile the
top card of each player's library, then you may
cast any number of spells from among those
cards without paying their mana costs.
Unfortunately for living beings on Ixalan, Etali finally
found a mount he would not crush.