How to access vanilla save data?

[Hipposgrumm]

I want to access a certain data value (EndDragonFight.previouslyKilled), but I can only find tutorials for saving and loading data from your mod. I have seen similar mechanics that I don't know the code behind but I'm pretty sure this is possible.

[ChampionAsh5357]

The parameter can be obtained from EndDragonFight#hasPreviouslyKilledDragon which can be obtained from the ServerLevel#dragonFight assuming the ServerLevel is the END which can be obtained from MinecraftServer#getLevel.

[Hipposgrumm]

The thing is, what if I want to access this value from the overworld or the nether (or some other dimension added by some other mod), how could I do that?

[ChampionAsh5357]

That's the point of MinecraftServer#getLevel. You can get the server from any current ServerLevel instance via #getServer.