Some of them have powerful abilities that can lock out an entire opposing strategy, such as Gaddock Teeg
Green is able to get creatures (and lands, although this ability skips lands) from the top of the library while white is able to get artifacts, enchantments, and planeswalkers
The haste is a great addition as well
Pair those great abilities with its excellent Esper color identity and low casting cost, and you have a Commander that can head up a ton of different lists
The card appeared in the initial reveal video for the drop, but then wasnt pictured in the drops lineup on the official website
Tribute Summoning Erebus The Underworld Monarch on the opponent's turn, if timed right, can completely shut down the rest of their turn and force them to pass back to you