My version of Herex:

Herex is the chief bio scientist of the crimson order, he talented in genetic engineering and was able to alter the genes of normal oil slime, making their fluid toxic to knights while harmless to Gremlins. The next chapter in his legacy however, envolves much more than single cell organisms, Herex is going for the big one, inorder to out-compete rezwog(yep, he cheated death)'s latest Dreadnought class mecha knights( armed with plate shield and 5*brandishes ) he decided to make Baram, Seerus's son-in-law, into a mutant SUPER gremlin!

Mission:
After beating trough a firey tunnel filled with toxoil, the knights will come to face razwog and his Dreadnought mecha knights, these mecha knights have the defence like a trolljan, which means their shield won't break after being shot by guns, Their attacks are similar to that of Arkus and they can also do the 360 swipe like a regular mecha knights. In the boss room, there should also be respwaning turrents as will as retrodes.

After defeating 2 Dreadnought mecha knights, Razwog will submit and claim he is forced to invent machine for tinkinzar and surrendered to the knights without any resistence, Feron, arriving on the scene, didn't trust Razwog a single bit. The knights entered the next ele while seeing Razwog is getting arrested.

Next lvl, Herex, like Seerus, will speak to the knights on a TV, "Foolish knights, leave now or this frozen chamber would be your grave"
Soon as the knights entered a cooling chamber, knights are encountered by a new breed of enemy, ICE slimes, the latest creation of herex, these slimes will create an ice mist upon death(like a icejelly) But the bad part is, when they merge into a colony, the spike shot off by the colony can inflict freeze status(if they became a largo, the gorund spike will also freeze, yep, swordies are screwed).

After surviving the chamber, the knights are encountered by Vaelyn, who is being apparently mind controlled by parasites, She is the boss for this lvl, the parasites can cloak but do not attack, the real danger is vaelyn, her attack includes a 3 step attacks with her flourish, she will continue the same move twice and then perform a bullrush across the room like a deadnaught and can also throw her flourish, she will be vulunerble once she threw both of her flourish(she will always rev after knocked down, but this gives u precious time to find the parasites) after killing all the parasites, vaelyn will return to her consiousness and point to the next ele.

After proceeding to the next level, the lvl is infested by darkfan and mortarfires, but this time around, mortar shoots toxic gas canister, dealing less elemental damage and poison status. After beating through the gremlin entrenched positions. Herex speak up again, "Greetings once again, spiral fools, it is time to meet one of your own."

After entering the next room, the party is faced off by a spiral demo, after a bit of conversation, he claimed that he was the original survivor of the compound 42, his entire squad perished in the compound and he was badly wounded, ever since then he always see visions of a world filled with flame and explosion, he want to make the vision come true, by blowing your paty sky high. He fights like a gremlin demo and is elemental resistant but not resisdant to piercing and shadow. After killing him, like Arkus, the anguish in his eyes faded as the knights exited the lvl.

The last lvl, after grinding through more toxoils and largos, the knights finally meet up with Herex, "ha, you made it this far, you will be the perfect subject to my next gremlin-knight hybrid experiment"( DUN DUN DUN!!!!!) Herex, armed with chainsaw blades on both of his arm and the latest gremlin stealth tech, he is literally a ghostmane stalker on steroid. Yep, that is all I can come up with...to be continued?