Oops! Half-demon au rambling because Spaz is just the source of my fucking brainrot now:
Oh ffs here he go again. To the DMC fandom: I deeply apologize.
If I have to suffer so do y'all: @polarspaz @laf-e-taffy @quasar-crew @thesmi1ingcheshire
OKAY, so I'm gonna be skipping to the first DT because that's just where my thoughts are being drawn, but! Here's some… basic stuff to lead into it.
So Leon obliviously wins his battle of wills with the demon parasite during the De Lago fight, then passes out as the demonic power settles within its new master. What happens to the (probably embarrassed as hell) demon? Uhhh… no clue but let's just say it merges with his body/soul, leaving no visible trace of it being there.
While Luis guesses it's the Plaga, even he's skeptical of that idea. This is because even though the Plaga are freaks of nature, they're still from earth and not spiritual in any way (despite what Saddler might say, the Plaga are fucking animals). The demon (and now Leon)? Nah, we're going full horror movie tropes with it.
Earth-born creatures can sense when something's off, ala a dog barking at a ghost. Demons are no exception to this, so Luis and Ashley can both feel that something is wrong on a basal level, but they can't tell why exactly.
The first time Leon fully Devil Triggers is during the Verdugo fight; he's out of ammo/separated from his guns, and the big bastard has Luis and Ashley (it wants to kill Luis, but obviously spare Ashley).
Leon S N A P S, blue demonic energy encasing him as wind and lightning roar.
The Verdugo doesn't have time to react; one moment Leon is yards away from it, the next the damn thing's arms have been ripped off and it's sliding across the floor.
Leon kills the thing with terrifying ease, and for a split second, Luis and Ashley are afraid he might turn on them.
Then he turns to them and asks, in a creepy and warped voice (but still unmistakably his own): "You guys okay?"
Leon didn't even really notice that he'd changed until one of them points it out, and then he starts freaking the fuck out because what the fuck???
The release of his Devil Trigger basically unlocks superhuman speed, strength, healing, and endurance in his human form (Leon got a slight buff pre-Trigger but it was barely noticeable, now he has to be very careful or else something's getting cracked like an egg).
He isn't pleased, to put it lightly. Especially that one time when, upon needing to jump up and climb something, he instead cleared the climb by several dozen feet just by jumping.
At least Luis can confidently say it isn't the Plaga?