Rule 712.4 tells us all we need to know: While a double-faced card is outside the game or in a zone other than the battlefield or stack, it has only the characteristics of its front face. Its the only face we can evaluate for commander-ness
You can activate Soul Drain by paying 1000 life points
Its a big flier that copies that spell, or another spot removal you have, while getting some counters
Will of the Temur I value modal spells quite a bit, and though Will of the Temur only has two modes, the ability to target any permanent with the first, and any player with the second is super strong
A crucial part of Legacy Goblins and Death and Taxes, it was also a big role-player in Modern Death and Taxes lists, as well as Merfolk decks, though the Vials time in Modern has mostly passed