The bottom half of the card feels sparse in comparison to the gorgeous art going on above it, and it would have been nice to see a bit more of a merging of the two
Because many of these effects also hit multiple targets, you can target an additional ETB creature and generate tons of value in the process
Due to the nature of his exile ability providing him with +1/+1 buffs, Umbris gets quite high power/toughness consistently, causing you to have a lot of free building space to slot support and pet cards, or cards that are nightmares or horrors by accident that just happen to work very well with his exile effect
Being a dragon rather than a dinosaur opens all sorts of dragon synergies, and making a 5/4 token on the enrage trigger is very strong
In gameplay, the legend rule means you can only control one legendary permanent with the same name at a time, reinforcing the idea that these figures are truly one of a kind