Saheeli, the Sun's Brilliance + Mana Echoes + Signpost Scarecrow + Breaching Hippocamp

Saheeli, the Sun's Brilliance

Mana Echoes

Signpost Scarecrow

Breaching Hippocamp

How it works

1. Activate Saheeli by paying and tapping it, creating a token copy of Breaching Hippocamp with haste.
2. When the token Breaching Hippocamp enters the battlefield, it and Mana Echoes trigger.
3. Resolve the Breaching Hippocamp trigger, untapping Saheeli.
4. Holding priority, if you control less than four creatures that share a creature type with Breaching Hippocamp, 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 Breaching Hippocamp for each trigger resolved this way.
6. Activate Signpost Scarecrow twice by paying 4, adding .
7. Repeat.