Delirium — As long as there are four or more card types among cards in your graveyard, Dragon's Rage Channeler gets +2/+2, has flying, and attacks each combat if able.
Nice! A new uncommon staple for Modern and Legacy. Super Powerful, the card gets boosted with strong evasion (that is flying). Super sweet balancing to make sure it is a must 4-of for Delver Decks, but not overpowered. Plus a great artwork. For me as a UR player in both Modern and Legacy, this is yet again a nice gift from Wizards following on the footsteps of Expressive Iteration. Well done!
@Joven it's not that hard. Dragon Rage will see play in decks that get Delirium quickly. We have Fetches, Mishra's Baubles, Surveil on her own and instant/sorceries. If you don't do something fast about her. She becomes an serious threat. Also she enables more graveyard matter decks. Good card overall. Let's see where it goes. I also think she's good in Jund, Delver and things like that.
For an aggressive deck it probably takes too long to achieve Delirium. Also, hard to make it consistently. Also, graveyard hate is omnipresent.