Whenever Umbris, or another Nightmare or Horror, comes into play under your control, you can take a chunk out of an opponents deck, with every card exiled feeding back into Umbris stats
Even better, your deck will be in the three best colors to make the most out of your tokens, both in giving them bonuses and making more of them, so you'll never be short of tokens to use
Creatures you begin to control later in the turn won't gain vigilance or get a +1/+1 counter
They make great intro decks for Magic and are perfect jumping-off points for any player looking to dive into either of these tribes
I've got another landfall leader for you, Omnath take 2
Regardless, its a masterfully drawn image of a pensive, regretful Beast with the card effect brilliantly shifting from a giving, loving suitor to a vengeful, raging monster