Permanents with Warp (and while they're mostly found on creatures, any permanent can have a Warp cost) allow you to cast them from your hand for their warp cost and exile it at the beginning of the next end step - remember, you can't cast for Warp as an instant ability unless the card has flash - which means these cards will usually have a nice enter the battlefield effect
Play single-pack, constructed, or triple-pack - online or solo
At rank 4, it is also a monster that can simply hit a catastor without a surprisingly small amount of entanglement
Ramp's sibling in cost reduction means The Darkness Crystal might not belong on the list, but is very welcome for a similar effect, and this card so happens to be a cool way to spend extra mana and get very real benefits
Buyouts on June 13 and July 12 raised the average number of copies per buyer to 8.0 and 6.0 (respectively), causing Victini XY 117s price to finally spike on July 19 when the Marketplace ran out of copies under $25