how do you kill thunder and the other

make sure your team is set up properly (element/team order, proficiencies, equips)

Looking at Golden and Rainbow (the pets currently on your team)
> Golden, as a shadow pet, should be in slot 1 as tank. As a shadow element (a magic/int element) and a tank, she should be equipped with gear that boosts her Int and Agi stats (Illusionist gear)
As it is, she has two Strength-type equips (Myrmidon armor, Assassin bracelet)

> Rainbow, as an air pet, should not be in slot 1, as he's an Attacker element. As an air pet (physical/str element, dedicated attacker type) he should have Str/Dex equips (Myrmidon).
Currently he has two Intelligence-type equips (Illusionist relic, Arcanist armor)- the relic especially is letting him down (Relics give a respectable boost to a pet's Damage stat, but since this is an int-type relic it's boosting his Magical Damage stat instead of his Physical Damage stat. As an air pet he doesn't use the magical damage stat at all, so he's losing out on at least 47 damage output.
Just look at his damage stats: Physical Damage: 24 / Magical Damage: 80. His attacks are calculating their output with the Phys Damage stat, so his attacks are way, WAY weaker than they would be with the correct equips)
You might also want to swap him to 1str prof rather than 1hp, but it should be okay as is.


You might want to check the broker for some lv20 rare or epic Illusionist and Myrmidon gear for them (although with them so close to lv25, it might be more worth it to just get them to 25 and go full lv25 legendary?)


At the very least, equipping Rainbow properly should make a significant difference to how fights go (meaning the fight against Cereth's pets should go rather more smoothly).