As a player declares a creature as an attacker, they may choose to have it attack a battle if its protector (not its controller) is a defending player
Illustrated by: David Martin Multiverse ID: 157972 Not Legal Traditional Standard Not Legal Traditional Alchemy Not Legal Traditional Explorer Not Legal Traditional Historic Not Legal Traditional Timeless Rulings 2008-08-01 Spelling this out completely: Each opponent who controls more creatures than you can't play creature cards
Since then, the number of four-color legends has more than doubled, with another three being printed across products in 2023 alone
Chandra's Embercat and Chandra's Triumph are reasonable spells that become stronger when Chandra enters the picture
Your Relentless Rats gets stronger the more copies of it you have in play, so if you have six Relentless Rats, each one of them is getting +5/+5, making them a three mana 7/7
But doing both and giving this blue creature flash is just distasteful, to the point where I question why people would even want to play this in a Cube environment