There's a mod called More merged trinkets or something that adds a couple of trinkets that are very powerful, one of those I think gives you 2.5 health per second. While probably not immortal on its own, you can combine it with other trinkets in the mod that should make you excessively powerful.

Thank you @Auren Wolfstein. That is a good idea thanks. Appreciate your input.

Originally posted by Auren Wolfstein:

There's a mod called More merged trinkets or something that adds a couple of trinkets that are very powerful, one of those I think gives you 2.5 health per second. While probably not immortal on its own, you can combine it with other trinkets in the mod that should make you excessively powerful.

Or, you can just hop on over to:
..\ Steam \ steamapps \ workshop \ content \ 1169040 \ <Mod ID>
Locate the file containing the item, and alter it's Buff to values you like.

However, i do NOT own this game, so i would not know. I'm just guessing based on what i read thus far of the game.
Seems somewhat easily modifiable. So mods might be even easier to modify. Enjoy experimentation.

This is as far as my "help" will go. Good luck.