The List rotates with each set, so the available cards change regularly
You can only do it on your own turn, so you cant tap it pre-combat, untap all your Myr, and then keep them up untapped to block and then activate Urtet on defense
Being an un-counterable 5/5 flier is a decent start, though the mana cost is tricky
(They create a Clue token.) II, IV Create a 2/2 black Alien Angel artifact creature token with first strike, vigilance, and Whenever an opponent casts a creature spell, this token isnt a creature until end of turn. Illustrated by Colin Boyer Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Legal Comp
First, you have to complete a Dungeon, the new flavour mechanic in Adventures in the Forgotten Realms set
Does this mean we should expect to see an officially sanctioned version of Sharpie Cube at some point in the future