Nim Deathmantle + Coretapper + Magistrate's Scepter

Nim Deathmantle

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. Nim Deathmantle triggers, causing you to pay 4 to return Coretapper from your graveyard to the battlefield and attach Nim Deathmantle to it.
4. Resolve Coretapper's 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. Repeat each turn.