While there are plenty of spells that can give negative stats to your opponents, Kaervek is great since it's a permanent ability, meaning unless either Maha or Kaervek gets removed, your opponents will be locked out of creatures
Its one Move, Vine Whip, also has just enough damage output to take down many Pokemon that become threats down the line, such as Charmander, Staryu, and Froakie, in only one hit
Firstly, it's a rare card on the MTG Reserved List, which means there are limited copies, and Wizards of the Coast will never print any more
A 3/5 flier for four is already close, and it a good distribution of stats in this world of Stoke the Flames, Roast, and Elspeth, and this ability is just awesome
Each celebration ability has a different effect
What really makes the Radiant Blastoise card great, though, is the artwork by Masakazu Fukuda which perfectly captures the classic retro design of the Gen 1 Starter from the earlier games