I have been stuck in the forgotten tomb, and have tried to defeat king Desius (or whatever their name is), about 5 times now and have only gotten them down to 83% health before being defeated. I just want to know if I need to have higher level pets or am missing something here

Team:
3rd slot, light attuned
2nd slot, fire attuned, trying to get higher level gear
1st slot, earth attuned

Did you successfully activate the seals? Activated seals debuff Desuis, making him easier


Additionally, For the most part you might want to replace as much of the gear as you can with lv25 legendary stuff, or raise the last three levels to hit lv50 on the three of them and get lv50 epic or legendary gear.
The rare and uncommon-tier gear really won't be helping, especially the relics (for comparison's sake, Purpurea's relic is lv35 uncommon, with a +75 bonus to the damage stat, Chaenomeles, lv25 epic, +105, and Albomarginata, lv35 rare, +110. A lv25 legendary is +135, beating out the highest of the three by 25 points. A lv50 legendary gives +260.

If you need equips, I'd suggest having pets do missions (you can check the mission pets and missions guide out in the player guides forum if you need to); lv25 very hard esior's haven missions, and lv45 Hard and lv50 Very Hard sanctuary of Saerielle missions can provide stuff that will help via their mission satchels (and if you get exceptional completion, then you get two mission satchels from that mission)
(gold, healing items, and epic+legendary gear- sending mission pets out is a good habit to get, especially once you have all 6 mission slots unlocked)

The equip types that you're using are the correct ones, all good there, it's just the level+rarity that's lagging (for clarity's sake, both level and rarity of gear affects the stats, and uncommon gear is, how to say,,, absolute trash, stats-wise, regardless of level. if you had a choice between only equipping a lv65 with lv65 uncommon gear or lv25 legendary, you'd want the lv25 stuff because the uncommons are just that bad)

Thank you! Ill get my hands on some better stuff. I couldnt figure out the seals unfortunately, Im super dyslexic and language stuff is really hard for me.

I leveled up to lvl. 53 before defeating desius with myconid fights in fungus grove. (only when they attack)

The seals require an active stat of 200+ when disregarding equipment bonuses
(so base stat+level bonus+proficiency bonus; you can check what a pet's stat makeup is if you hover over their active stat (for clarity, on a pet's page the stats are displayed as "Stat name: active stat (base stat+grove bonus stat)")

With the pets on your team you could only do the Int seal (with either your light or fire), but a common trick is swapping Mission pets in when a seal is reached

in order of encountering them the seals are:
agility, strength, dexterity, intelligence
I'm not entirely clear if you can go back and retry? I feel like that was a maybe thing?


(admittedly for Desius fire isn't strictly the offensive element you want, since fire is predominantly a multi-enemy attacker, where air is predominantly single-enemy focus, but it can be done, probably just takes longer)

You can go back and I will definitely do that, thank you!