Grim Harvest + Coretapper + Magistrate's Scepter

Grim Harvest

Coretapper

Magistrate's Scepter

How it works

1. Activate Coretapper's first ability by tapping it, putting a charge counter on Magistrate's Scepter.
2. Activate Coretapper's second ability by sacrificing it.
3. Grim Harvest's Recover ability triggers, causing you to pay 2 to return Grim Harvest from your graveyard to your hand.
4. Resolve Coretappers ability, putting two charge counters on Magistrate's Scepter.
5. Activate Magistrate's Scepter's second ability by tapping it and removing three charge counters from it, taking an extra turn after this one.
6. Cast Grim Harvest by paying 1, returning Coretapper from your graveyard to your hand.
7. Cast Coretapper by paying 2.
8. Repeat each turn.