So I'm in the Forgotten Tomb, and I encounter... Seals?
What are they for? Do they help me defeat Desius?
Because I fought him, and I was defeated, and he had these power ups, something to do with broken seals?
How do I unlock them? I'm really confused right now. The inscriptions really didn't help me at all. I didn't know what they meant at all.

Help????

Successfully activating all the seals removes his buffs.
The only time you can tell if you've successfully activated them all is when you get to the last of the four and it lights up.
Each seal has text telling you just a little about the seal- you have to translate it, and use a pet that has the right stat.
You probably need ~300+ in the specific stat it wants? It could be it needs 200+ in the stat discounting the pet's equipment bonuses? If the pet has over 300 in the stat the seal wants it should be all good (you can just reassign prof points or swap out pets specifically to do the seals.)
Anyhow,
courage = strength
perception = intelligence
cunning = dexterity
alacrity = agility
You can highlight ^this space if you need the spoiler for which word means which of the four stats.