Karumonix, the Rat King has a similar role but offers a poison wincon instead of extra damage, while format classic Marrow-Gnawer fixes your lack of evasion and can generate a ton of extra bodies even if those tokens wont contribute to or benefit from the Relentless Rats effect
That said, having to wait 2 turns for your payoff isnt always a bad thing
(Equipment, Auras you control, and counters are modifications.) Creature - Fox Samurai Ramp (CTRL to add secondary) Removal Plasma Caster Equipped creature gets +1/+1
The static ability seems really powerful and could be game-breaking in other formats, but I dont see a Legacy archetype that can really harness its power
Give Black Mage Lifelink with White Mages ability, however, and it becomes truly monstrous
This means, should you have Gorion and Lucky Clover in play, each Adventure spell will trigger Jadzi three times