Moxite Refinery + Magistrate's Scepter + Mossborn Hydra + Izzet Boilerworks

Moxite Refinery

Magistrate's Scepter

Mossborn Hydra

Izzet Boilerworks

How it works

1. Play Izzet Boilerworks. When it enters, it and Mossborn Hydra trigger.
2. Resolve the Izzet Boilerworks trigger, returning it from the battlefield to your hand.
3. Resolve the Mossborn Hydra trigger, doubling the number of +1/+1 counters on it.
4. Activate Moxite Refinery by paying 2, tapping it and removing three +1/+1 counters from Mossborn Hydra, putting three charge counters on Magistrate's Scepter.
5. Activate Magistrate's Scepter's second ability by tapping it and removing three charge counters from it, causing you to take an extra turn after this one.
6. Repeat each turn.

This loop achieves an engine for infinite turns by using Moxite Refinery as a bridge to continuously charge Magistrate's Scepter. Every turn, you play Izzet Boilerworks, whose landfall-like entry trigger and bounce mechanic combine with Mossborn Hydra to rapidly multiply its +1/+1 counters. Moxite Refinery then converts those surplus counters into the charge counters that Magistrate's Scepter needs to grant you endless extra turns.