Harold had two ideas, for this task he was put to. One was simple, short-term and much more easily executed; the other more complicated, probably overkill, but likely more stable in the event that it would be some time before they could track down the rift.

Shooting the Denubae with something was simple, but everything he thought of either the immune system seemed like it could shoot down, or it was mechanical, and the power source would just feed them and then be snuffed out.

"Make their footprints glow," Scotty had said. Harold was pondering on that.

His first inspiration was the time Vanessa proudly shoplifted a shirt just to have the thing ruined by UV dye in a loss prevention tag. She'd been so damn cocky about her ability to get the thing off and ended up with the crap everywhere.

So... maybe they could literally make the f*cking footprints glow. Make a f*ckoff big... device. An arcane device to lure a bunch of them some place, and on activation, it would explode with UV reactive dye, coating the things. Water killed them, so it was a fine line; they'd have to find a paint based in oil or something similar. For that matter...

Aye. Heat-set oils never dry at all unless they're baked. It would just... drip off until it was gone, meaning if they got enough of it on the thing, it might last long enough to trace back. Harold wasn't sure, but he wrote down the possibility of a traceable mineral or metal mixed through the dyes that could be scanned for, rather than just visually chased.

The long-haul idea found inspiration in an acquaintance in the other-place.

He'd flipped through all of Scotty's books, his mind wandering on various possibilities.

A bacteria seemed the natural thing, as Scotty suggested, considering that bioluminescence occurred naturally in that form. It seemed like something too easy for an immune system to recognize and flush out. Nor could he figure a specifically trackable means for it to present that wouldn't be transient.

The longer they could light up these things like roman candles, the better the chance of keeping track of them long enough to find that rift.

It was the word 'nanoprobe' singing out in his mind from the memory of that man that had him sifting through types of diseases. No, it would be better as something that self-propagated and could coast underneath the radar of an immune system. And if he could finagle something that actually spread from one Denubae to another, giving them as many footprints to follow back to their origins as possible, even better. He might even land a bonus of making the animals sick, weakening them. That left a genetically engineered virus or a parasite, and honestly, he had no idea how they would go about doing something like that.

A virus of that kind seemed too easy to transmit to any potential victims of the Denubae through venom, so he struck that.

That left a parasite. It was a little chirp from Grace that had him off on another book-flipping tangent; were there any parasites that fed on animals that luminesce? There were. The vast majority seemed to exist in the sea. Maybe they wouldn't have to engineer anything.

...this was not a fun topic to research, and Harold found himself... quite glad that he trusted Scotty's hygiene in the kitchen. He struck off a multitude of gruesome possibilities - how the hell was he going to sleep tonight? Buh - before landing on one that seemed to be a winner.

Lung fluke. It existed on Earth, but whether this version was a parallel kind that had evolved on Rhy'din or it had world-hopped here and evolved, there was no information. Common in crabs and other kinds of seafood on earth, in the oceans of this planet some unrecorded time ago it had apparently latched on to a type of bioluminescent shrimp and come to share the trait.

Compared to the Terran version, it was f*cking frighteningly awesome. It multiplied with horrific speed, and in this version's case, lung fluke was a misnomer; it was a full-body fluke.

Paragonimiasis could exist quite happily in mammals and would present in the feces and sputum of the animal. Additionally, it could be cured by anti-parasite drugs should the infection somehow transmit to someone during an attack. The parasite could exist in dogs, so if the Denubae were more biologically similar to canines, it could still work.

Essentially, they could make the Denubae sick, and follow the trail of glowing snot, sweat and crap back to its lair.

Not, perhaps, delightful. But hopefully effective, with several advantages. No guesswork as to how it would present, little danger to bystanders so long as they sought treatment, the organism would multiply and hopefully spread through the species, and it would even weaken the animals, all at the same time as leaving a glowing trail back to wherever the things came from.

The first trick would be getting hold of some of the infected shrimp; it didn't appear to be a widely-caught animal, but they did exist in the seas off this continent and wouldn't be difficult to lower a net for. The second would be incorporating the parasite into something the Denubae would want to eat. The third would be the wait; freaky propagation time or not, it would still take time for the organisms to multiply to the point of being visible, but it would eventually become so pervasive as to even infect the skin, lighting up their hides as well as their excretions.

All of this... providing they were susceptible to such a parasite.

Harold sighed when he finished writing out the idea for Scotty to look over, hitting his books again for other possibilities.