Rex, Cyber-Hound + Pili-Pala + Sage of the Maze

Rex, Cyber-Hound

Pili-Pala

Sage of the Maze

How it works

1. Activate Rex using Sage of the Maze's ability by tapping it, adding two mana of any color(s).
2. Activate Rex using Pili-Pala's ability by paying 2 and untapping it, adding one mana of any color.
3. Repeat.