Master Transmuter certainly falls within the category of the best Magic card art of all time, and you should feel honored to have it set as your computers wallpaper
It functions as a card advantage engine, allowing you to trade your small critters in for cards and the drain ability can straight up win you the game
When Arna Kennerud or any other modified creature attacks you get to double the number of each kind of counter on them, as well as make a duplicate copy of each nontoken permanent attached to it
By filling your deck with Angels, Demons, and Dragons with these types of abilities, you can free up slots that you would use for instants and sorceries with the same effects , getting them for free with an attacker instead of casting them
Dealing with an Ulamog once it is in play is a bit of a pain for your opponents too, since if they want to target it with any sort of spell or ability, theyll have to sacrifice two permanents as part of its ward effect