Svella, Ice Shaper + Roxanne, Starfall Savant + Agatha of the Vile Cauldron + Umbral Mantle

Svella, Ice Shaper

Roxanne, Starfall Savant

Agatha of the Vile Cauldron

Umbral Mantle

How it works

1. Activate Svella's first ability by paying 1 and tapping it, creating a Icy Manalith token.
2. Activate the Icy Manalith token by tapping it, adding 1.
3. Roxanne's second ability triggers, adding 1.
4. Activate Svella by paying 1 and untapping it, giving it +2/+2 until end of turn.
5. Repeat.