Magistrate's Scepter + Contagion Engine + Lithoform Engine

Magistrate's Scepter

Contagion Engine

Lithoform Engine

How it works

1. Activate Contagion Engine by paying 4 and tapping it.
2. Holding priority, activate Lithoform Engine's first ability by paying 2 and tapping it, copying Contagion Engine's ability.
3. Resolve both Contagion Engine abilities, putting four charge counters on Magistrate's Scepter.
4. 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.
5. Repeat each turn.