Swords to Plowshares (T1, Ext, S, Block) Black and red are both known as being the colors of creature removal, so it's ironic that Swords to Plowshares should be hands-down the most powerful single-targeted creature removal card in all of Magic
Mothman is maybe one of my favorite 'new' commanders because his mechanic works well with his theme, and making a mill deck may also make him into a huge beater, which gives you options for how to approach a win condition in the event that Mill is not going to work by itself
That could be a card like Davriels Withering, which perpetually gives a creature -1/-2 if that card reduces a creature to 0 toughness or less and sends it to the graveyard, for example, the debuff will remain in effect even if a player is able to bring it back to battlefield (causing it to immediately die again)
If you can keep it alive for long enough and mill enough cards, Consuming Aberration becomes beefy enough to wipe the floor with other players