Maeto True Form

The Idle Transfiguration passive is very similar to Bumta's Copy Technique, but it procs even faster, and more importantly, it can theoretically stack (depending on the attack speed).

Maeto's Soul Manipulation works great as a finisher, and it pairs well with some AoE-based units to clear up the wave after another unit has cut into their HP.

Maeto's kit is kinda basic for a secret unit.

A few more passive and active abilities would make him a more interesting and overall stronger unit.