You can then cast that card for as long as it's exiled, though you have to pay the mana cost, colors, and all, which is why the Treasure tokens are so important with Rev
Its like spending an extra mana to Time Warp twice and you have no restrictions on what you can copy
I do wish it helped you get descend, so it was both a payoff and an enabler those often make the best signpost uncommons, but its such a good payoff for loading the graveyard with permanents that it still looks like a nice signpost Uncommon Exploring whenever you gain life is something Im interested in, especially on a two mana 2/2 with Ward Pay 3 life
I was glad eldrazi got some love, but I have not been impressed with this what looks like a big mana commander
Finally, if you hit 20, you get to copy each card exiled with Wizards Spellbook and then cast any number of the copies without paying their mana costs