Lighthouse Chronologist

In a four-player game, if you have a level 7 Lighthouse Chronologist and there are no other extra-turn effects, the game will proceed like this (with extra turns in brackets): your turn, opponent A’s turn, [your turn], opponent B’s turn, [your turn], opponent C’s turn, [your turn], your turn, opponent A’s turn, and so on. The same principle applies to a multiplayer game with a different number of players.

A creature’s level is based on how many level counters it has on it, not how many times its level up ability has been activated or has resolved. If a leveler gets level counters due to some other effect (such as Clockspinning) or loses level counters for some reason (such as Vampire Hexmage), its level is changed accordingly.

In a two-player game, if you and your opponent each control a level 7 Lighthouse Chronologist, they’ll essentially cancel each other out and you’ll alternate turns. Since all the turns you’d be taking are extra turns created by these abilities, make sure you know whose normal turn is supposed to be next in case one or both of the Lighthouse Chronologists leaves the battlefield.