World Eater's like Hektor hate the Nails, and are going to fear them fiercely once they've been temporarily healed, and will, by sheer necessity if not genuine gratitude, fight for the Liberator. How heartwarming!
Except, to anybody else, it looks like Cain, scheming mastermind, has found a way to make Khornate Berserkers dependent on him. He's made them drug addicts hooked on his supply. Oh, what wicked cruelty! Abaddon impotently rages that he never came up with a plot this effective!
To use a Star Trek analogy, Cain is a founder, the World Eaters are Jem'Hadar, and the Panacea is Tetracel White. If they run out of the stuff, they revert to a state of homicidal rage and uncontrollable bloodthirst. Like, you could perhaps copy that imagery, with every World Eater having a tiny pouch on their armour where the daily Panacea dose is inserted, and a thin pipe directly injects it into their neck.
Expanding that, Emeli's Handmaidens could be the Vorta-analogue, perfectly good-mannered minions that deliver the daily dose of White Panacea to the reformed World Eaters.
The squad of World Eaters knelt. "We pledge our loyalty to the Liberator, from now until death!"
Krystabel smiled as she picked five doses from the box and distributed them. "Then receive this reward from him, so that it may it keep you strong."
The ancient Astartes shuddered with bliss once the connection was restablished and the fluid flowed to their necks through transparent cables. They rose as one, each punching their chest. "Victory is life!"
Meanwhile, off to the side a Valhallan, USA trooper and a BORG all watch the ceremony;
BORG: "They do know they can have more than a days dosage, right? I mean we have literally warehouses full of the stuff. It's a precious resource, but in the same way fuel is. We have more and they can have more."
Valhallan: I'm still getting used to the idea that we literally have warehouses full of a medicine that cures almost everything short of death. Regardless, I can't imagine that they don't know by now. That seems like the kinda thing you'd have a hard time hiding from the genetically enhanced demigods.
USA Trooper: I think they just really like the ceremony. Kinda makes the whole thing feel really special and meaningful.
BORG: But it's so inefficient! They should have a months worth of the Panacea prepared in an auto-injector so they don't have to go through this whole thing every day or so.
Valhallan: Yeah friend, that would likely be a lot more efficient. But they seem to like it this way and I'm not exactly inclined to try and tell the former blood-maddened Berserkers that I do think they're doing their ceremonies wrong.
USA Trooper: That and the Handmaidens also seem fond of it, and I'm even less inclined to try and argue with them. World Eaters can kill you, but I've seen Lady Emili first-hand and I'm not getting on her bad side.
BORG:… Fair points. This battle might not be worth fighting.