Ultimately, like all MTG cards and price spikes, Umbra Mystic could easily go either way in the long run
Its primary utility lies in its ability to reduce your life cards to a low enough count to activate the healing effects of cards like OP04-112-yamato-722, OP07-119-portgasdace-342, and EB02-052-enel-901
Instant-speed Grim Bounty is a great way to deal with the format's biggest threats and the treasure could help ramp or splash
Some kind of prominent central logo or design couldve neatly filled the space, in the same way the last Transformers movie filled the space where a critically-acclaimed blockbuster could have been
If you play an Amulet turn 1, you can tap the land you already have out on turn 2, play a bounce land, return the tapped turn 1 land to hand, then tap the bounce land for an extra 2 mana