Do I need the main Death Knights mod for this datapack to do anything?
Yes. This datapack only patches spell stats for the main Death Knights mod. Without that mod loaded there are no Death Knight spells for it to change, so it does nothing.
How do I check that the balancing datapack is actually working in my world?
Run /datapack list and confirm the pack shows as enabled. Then test it in game: Death Grip should come off cooldown noticeably faster, and Lesser Festering Strike's cooldown should be about half what it was.
Which spells does this datapack change?
The built-in changes target the Unholy path. Festering Strike gets more physical and magic damage, longer reach and a shorter wait between hits. Lesser Festering Strike gets more spell power and half the cooldown. Death Coil fires faster, harder-hitting bolts, Epidemic gains direct impact damage, and Death Grip has a shorter cooldown.
Does this nerf the other Death Knight specs?
The datapack focuses on buffing Unholy rather than weakening other paths. The other spells aren't boosted by default, but you can raise or lower their numbers in the config files to suit your playstyle.
I edited a spell file but nothing changed in game. What did I do wrong?
Usually the change wasn't reloaded. Run /reload or restart the world. Also make sure you edited the copy that is actually inside the world's datapacks folder. A single missing comma or bracket can stop the file from loading, so check your formatting too.
How do I set this up on a multiplayer server so everyone has the same balance?
Put the datapack in the server world's datapacks folder and enable it, then run /reload. Spell stats are handled by the world, so every player on the server fights with the same numbers. Any custom edits should be made to the server's copy.
What's a good Unholy rotation with the buffed spells?
Pull a target in with Death Grip, which you can now use more often. Then work Festering Strike and Lesser Festering Strike, taking advantage of their extra reach and shorter cooldowns. Fill gaps with the faster Death Coil bolts and use Epidemic for its burst of impact damage.
Will this datapack hurt my performance?
No. It only changes existing spell values and doesn't add new blocks, mobs or effects. The performance cost is effectively nothing.
Another datapack also changes Death Knight spells. Which one wins?
When two datapacks edit the same spell, the one loaded later in the /datapack list order takes priority. If you want this pack's numbers to apply, use /datapack enable with the 'last' option to move it to the end of the list. Alternatively, merge the values you want into one set of files.