The results of demon study:

Raiden: A number of tests seem to suggest Raiden has a form of crystalkinesis and is able to control crystallized aether, which brings back memories of the zombie things you fought when he was still hostile. The researchers find it fascinating and a bit horrifying. The power in question seems consistent with a rare type of Carbink mutation called Diancie. Diancies are elusive creatures formed from volatile Carbinks transformed with high pockets of aether. It's pretty likely that Raiden could learn certain rock-type moves or even power up his old Crystal Dust move with enough training. As far as his history, Raiden probably was one of the golems of Little Haven. Strangely, despite having recently evolved, his armor is scarred and retains blemishes that indicate weathering patterns, as if it was the same armor he wore before his regression. Signs indicate he used to be covered in thick moss and plantlife, suggesting he was separated from the other golems and shut down outside at some point.

Khamsin: Khamsin seems to possess a far stronger aetheric signature than any of the researchers expected. He's been imprinted on by multiple dream beings, which seems unusual as he didn't even hatch until you arrived. As a result, a sort of proto-personality seems to have formed in him even before his birth, a constant struggle between bloodthirst and desire for honorable combat. His potential seems to lie not only in Steel-type moves but Dark type as well, and it's likely he could learn to call forth power straight from the Aether itself with enough training. A truly intense amount of Hatred seems to have been present in his demonizing.

Meloetta: She can talk!

"I was born the last of House Muse, we entertainers of the Sindar. All of us Meloetta, as they branded. They called me the Siren as it was my voice that had the greatest power, but I was seventh among such names. My voice could charm man and monster alike and coin flowed in Yanahe'ya. The nobility would drink, and sing, and know each other, and I would be fed bread, candied fruit and on occasion the flesh of honored beasts who had passed into eternity. And then the end came, blood running through cracks in the stone. And even that vanished, along with all trace of my masters, leaving behind myself and the other forgotten souls. Only later was it that I heard a whisper that drove me mad with jealousy over humanity who thrived when my masters perished, jealousy that they still lived while I remained frozen in time, never to live the days of old. I know not if it was the beast in fine clothing who spoke that hatred into my heart, or if it was yet something else."

Her power as a demonized Legendary is enormous. She bears potential to sense and possibly even influence emotions in others or freeze them solid like ice. She is a fiercely competitive spirit, and actively seeks entertainment to fill the void left by the years. She's also willing to answer questions.

Katahala: Katahala seems to be in a very unique state at the moment. His parent demon was a strange cross of Ferrothorn and Metagross, demonized, and the strange experiment Zahara performed might have unlocked further latent potential in it and its offspring. That's possibly why, when exposed to Soma's fairy power, Katahala became a crossbreed of a different kind: Ferroseed and Lilligant. According to the type specialist researchers at the Runiversity, Katahala displays a very protective nature consistent with what they call Seelie-aspected fairies, but the root of his protective power is ingrained even deeper than that, possibly one of the powers passed down from his parent. His potential lies with Fighting type moves, and in particular, his Mighty Guard move may hide secret potential. A child of many worlds, united as a protector. His resolve is unshakable.

Baucis: Baucis spends some time debating with the research team. They've never seen this many demons capable of human speech before/ Baucis has this to say.

"Emotion, knowledge, willpower... my wild friends do not know these things, but I do. I am respected among them as a leader, and yet I still feel an outcast among them, uplifted to a place I should not be. What, then, is my lot in life? What am I meant to do with this enlightenment? Perhaps that was the true root of my rage. To know how different humans were, and to see them squander their gifts in abuse of my friends. They claimed our lands, poached our kind, gave little thought to natural cycles, population growth or decline. Many kill for sport, the thing I hated most of all. To take a life and then not even make use of the body. I, like this 'siren'-"
 - he seems to be referring to the Meloetta - "-felt a sort of whisper call my hatred to the forefront. I cannot explain it further. Now, of course, I know not all humans are this way. My friends are noble and compassionate, and they deserve my guardianship. I wonder, if my kind all had the gifts of humanity that I now share in... would humans be so quick to act as they do toward them?"

Baucis shows a high degree of intelligence even beyond the usual enlightenment that demons receive on their transformation. The researchers note his leadership ability seems to be both charismatic, and possibly a supernatural enhancement of his pack leader instincts - a trait that is consistent with the leader of the Hero Rune quartet, Cobalion. Baucis's power might manifest in the potential of powerful blade techniques, an aspect the researchers dub "All for One", as well as heightened teamwork abilities, which they dub "One For All". Their research shows a strange connection between Baucis and Katahala, as well, leading them to go back and study the plant to possibly have a power relation to Cobalion's lieutenant, Virizion.

Why demons seem to mimic traits of rare or True Rune pokemon isn't known at this time, but it gives a lot of weight towards why they were called demons in the first place. Savage pokemon, imbued with intelligence and malice, with rare or godly powers - what else would you call things with such terrible wrath?