You can set this loop off as early as turn 4, starting with [CCCCC CCEEE] as your first shuffle:
- Play 5xCopper, spend a Baker token, buy Travelling Fair topdecking 2xLurker.
- Play 2xLurker to gain a King's Court; buy a Donate, keeping KC+2xLurker.
- King's Court a Lurker to trash a King's Court, gain it and trash a Cultist (to draw the KC). Play the newly gained KC on the other Lurker, to trash a King's Court, gain it and trash an Overlord.
On turn 4, your starting hand is three King's Courts and two Lurkers, with one Overlord in the trash.
Play King's Court on King's Court on 2xLurker (and later King's Court).
The 2xLurker gain the trashed Overlord plus 2 more, then trash a Cultist.
Your hand is now 3xOverlord plus the King's Court you're about to play.
Play the King's Court (you have 3 tripled actions).
Play Overlord as Mining Village (trashing itself), Lurker (regaining itself) and Bridge.
Your hand is 2xOverlord and there's an Overlord in your discard pile. You have 2 tripled actions.
Play Overlord as Mining Village (trashing itself and drawing Overlord), Lurker (regaining itself) and Bridge.
Your hand is 2xOverlord and there's an Overlord in your discard pile. You have 1 tripled action.
Cost reduction is 2, so you're ready to go off. Repeatedly do this:
Play Overlord as Mining Village (trashing itself and drawing Overlord), Lurker (regaining itself) and King's Court.
Kingdom: Lurker, Bridge, Mining Village, Baker, Cultist, King's Court, Overlord (+ 3 more); Donate, Travelling Fair.
Footnote: really you only need to gain 2xOverlord; a starting hand of 3xKC+2xLurker with no Overlord in the trash will do just fine.