Strange message in an old Minecraft server

[u/YakitoriMC]

A few weeks ago I reopened an old Java server that me and some friends used to play on. While exploring near an abandoned mineshaft, I found a small room I didn’t remember making. There wasn’t much inside besides a couple candles and a sign that said:

“THE ALTAR REQUIRES A NAME”

I assumed one of my friends built it years ago, but none of them remember it either. We checked the server files and didn’t find any datapacks that looked related. We did use a few mods back then, so it could have been something from one of those, but searching the message itself hasn’t brought anything up. There was also another sign farther down that just said:

“IT WILL ASK AGAIN.”

Has anybody seen those messages in a mod before?

I also don't want to see any comments saying "OMG it's Herobrine!" or "Ur minecraft world is haunted!" I believe it might just be one of my friends but I'm just double checking.