The stat you want is "HP %"
Make sure to declare the stat as a predefined int before you use it, since it's not included in vanilla TL2.

The stat you want is "HP %"
Make sure to declare the stat as a predefined int before you use it, since it's not included in vanilla TL2.

Mind me asking why there's a need to do that? The HP % stat is a static stat already in the game, you can evaluate it with a stat evaluator?

Are there any other really useful stats like this that I should know about, and is there a way I could explore them on my own?

Yep, you need a declaration in MEDIA/STATS/ to associate a hardcoded variable in the executable with a stat object in the statwatcher system. Vanilla TL2 only declares a fraction of the accessible hardcoded variables (list), so you need to declare the others if you want to use them.

Three more notes that may be of interest:
1. The connection between a hardcoded variable and a stat object is one-way. You can read the hardcoded variable via the stat object, but you cannot change its value.

2. The a stat object is, in C parlance, volatile. Its value can change nonprogrammatically, in the middle of a function. If you need a guarantee that the value will be consistent over multiple reads, then you need to copy the value to a custom stat once at the start of your function and read from that.

3. Some of the issues with floats not working well with statwatchers can be overcome by declaring the stat object as a predefined int. The program seems to handle casting the float to int just fine in this context.