mtg umbris commander deck Umbris, Fear Manifest Mill Exile Nightmare Horror Tribal Magic Whenever Umbris or another Nightmare or Horror enters the battlefield under your control Umbris, Fear Manifest | Innistrad:

Her ability costs WUBRG, and it lets you put a Legendary permanent from your Library into play as long as its mana cost is less than her power

Thanks to this, according to EDHREC, Alela, Cunning Conqueror appears in around 64% of Maralen, Fae Ascendant decks right now

Usually they replace a common card to give you a random card from the set with a shiny foil treatment but again this can lead to an imbalance as my opponent might end up with 3 mythic rare cards if they get lucky with the randomiser

As for the latter, it gives you a way to deal with a lot of the most-played advantage engines in the format, like Rhystic Study and Smothering Tithe