Activate Coretapper's first ability by tapping it, putting a charge counter on Magistrate's Scepter.
Activate Coretapper's second ability by sacrificing it, putting two charge counters on Magistrate's Scepter.
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.
Deal combat damage using Celestine, causing you to gain three life.
At the beginning of your end step, Celestine triggers, returning Coretapper from your graveyard to the battlefield.
Repeat each turn.

Infinite turns

Celestine, the Living Saint

Coretapper

Magistrate's Scepter

Activate Timestream Navigator by paying {2}{U}{U}, tapping it, and putting it on the bottom of your library, causing you to take an extra turn after this one.
Activate Cellar Door by paying {3} and tapping it, targeting yourself, putting Timestream Navigator from the bottom of your library into your graveyard and creating a 2/2 Zombie token.
Declare Celestine as an attacker, dealing 3 damage and gaining 3 life when she does combat damage.
At the beginning of your end step, Celestine triggers, returning Timestream Navigator from your graveyard to the battlefield.
Move to your next turn.
Repeat.

Combos with "Celestine, the Living Saint"