Thu 04 Apr 2024, 11:31
Okay, so there are two things happening when you gain a level in the part you referenced.
First, you gain more hit points, which is (for the Origin you're referencing) either 1d8 + your Constitution modifier or 5 + your Constitution modifier. You can pick the 5 instead of rolling the d8 and taking your chances.
That is standard 5e and you can reference the Player's Handbook for more info.
You are also gaining another Hit Die, which you can use during a Short or Long Rest to recover HP, or to reduce Corruption. You use the Hit Die then, it's not part of gaining new HP for the new level.
Your new Hit Die is always the same die size (d6,d8, etc) as the die you could have rolled to gain hit points, but it is its own thing.
Gaining Hit Dice at level-ups and spending them to recover HP is standard 5e, but Ruins of Symbaroum Rests work a limitless differently, with Extended Rests working more like standard 5e Long Rests.
I hope this helps.