Deceiver Exarch + Mana Echoes + Saheeli, the Sun's Brilliance + Signpost Scarecrow

UR identity

Commander legal

The 4 combo pieces

What must be in place

Saheeli does not have summoning sickness.
{U}{R} available, plus an additional {U}{R} if you control less than three creatures that share a creature type with Deceiver Exarch

How to execute it

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

What the combo produces