Saheeli, the Sun's Brilliance + Mana Echoes + Corridor Monitor + Stonework Packbeast

Saheeli, the Sun's Brilliance

Mana Echoes

Corridor Monitor

Stonework Packbeast

How it works

1. Activate Saheeli by paying and tapping it, creating a token copy of Corridor Monitor with haste.
2. When the token Corridor Monitor enters the battlefield, it and Mana Echoes trigger.
3. Resolve the Corridor Monitor trigger, untapping Saheeli.
4. Holding priority, if you control less than four creatures that share a creature type with Corridor Monitor, repeat steps 1 through 3 one additional time.
5. Resolve all Mana Echoes triggers, adding C for each creature you control that shares a creature type with Corridor Monitor for each trigger resolved this way.
6. Activate Stonework Packbeast twice by paying 4, adding .
7. Repeat.