Mystery Booster Playtest Cards 2021

Jasconian Isle

(Jasconian Isle isn't a spell, it's affected by summoning sickness, it's blue, and it has "{T}: Add {U}.")
Jasconian Isle enters tapped.
Jasconian Isle doesn't untap during your untap step.
At the beginning of your upkeep, you may pay {U}{U}. If you do, untap Jasconian Isle.

Mystery Booster Playtest Cards 2019

(CARDNAME isn't a spell, it's affected by summoning sickness, it's blue, and it has "{T}: Add {U}.")
CARDNAME enters the battlefield tapped.
CARDNAME doesn't untap during your untap step.
At the beginning of your upkeep, you may pay {U}{U}. If you do, untap CARDNAME.