The (Un)Official Console Weekly Event Thread 2 (Current Event: Stormheim)

Specifically, VIP chests cost 5x what Gem chests cost, with 10x the payout for Legendary and Mythic troops. That doesn’t necessarily translate into 2x the odds of pulling one Mythic from a given set of keys, but it’s definitely more efficient than Gem chests are, if your aim is solely Legendaries and Mythics.