Cavern Harpy + Crystalline Crawler + Gemstone Array + Inexorable Tide

Mana needed: {U}{B}

UB identity

Commander legal

The 4 combo pieces

What must be in place

Crystalline Crawler has at least one +1/+1 counter on it.
Gemstone Array has at least one charge counter on it.

How to execute it

  1. Cast Cavern Harpy by paying {U}{B}.
  2. Inexorable Tide triggers, putting a +1/+1 counter on Crystalline Crawler and a charge counter on Gemstone Array.
  3. When Cavern Harpy enters the battlefield, it triggers, returning itself from the battlefield to your hand.
  4. Activate Gemstone Array's second ability by removing a charge counter from it, adding {B}.
  5. Activate Crystalline Crawler's first ability by removing a +1/+1 counter from it, adding {U}.
  6. Repeat.

What the combo produces