Not sure where else to post this but it was kind of a bummer. I came to the black bridge for the first time and no boss spawned. It looks like there should be a boss here. As far as I can tell no one else has been through this minecells instance. I relogged for a few hours in the Ramparts and when I came back to the black bridge I now get the "disarmed" debuff and I got the advancement "Finally, a moment of rest..." and I got the Black bridge dimensional Rune (didn't get any of those the first visit). The spawn obelisk is the only thing on the bridge and it says it requires the respawn rune to activate when I right click it.

Modpack:
All of Fabric 7 v2.5.0
Minecells 1.8.3

Server:
All of Fabric 7 official NA server

Lovin the mod thank you very much!!!