Describe the bug
I delayed my regen for the first time ever for about an hour to the point where it was killing me, while I was remapping the conflicted regen key it destroyed my character, I say destroyed because none of my items dropped, and a tombstone was not created, I was only left with my soulbound sword, all of my precious inventory was completely lost.

Expected behavior
Use normal /kill methods so that gravestone mods can be used to preserve inventory.

Regeneration-1.12.2-1.6.6
tombstone-3.5.4-1.12

Modpack - https://minecraft.curseforge.com/projects/drtardis-2-new-adventures

That shouldn't happen.

@Suffril as per this code snippet we're just attacking the player using a custom damage source (the expected way to kill a player for this purpose I'd think). I could understand a tombstone mod not creating one with this custom damage source, but shouldn't the items just be dropped then?
https://github.com/Suffril/Regeneration/blob/64ce67b5998bb0884186a9ef2d5756beab2e240e/src/main/java/me/swirtzly/regeneration/handlers/ActingServerHandler.java#L59-L71

Perhaps it's a good idea to test this without any tombstone-like mod, as it may be interfering.

This should not happen, as we do not do anything outside of what normal Minecraft does in terms of damage aside creating our own DamageSource type that extends vanillas. The only reason we do this is to have flexible control over the death message, this has no effect on gameplay to my understanding.

Have you tried making an issue with the Tombstone mod as well, as I have no real way to approach this

Just for our own observational purposes, could you make a video of the bug at all? This can be created on a flat world or whatever you prefer. To get back into this state without having to wait out the whole Regeneration process; You can give yourself regenerations as normal, trigger regeneration and then use /regen-debug fastforward (it may be fast-forward) after punching the ground

Thank you, will let you know if it happens again.