Damian Wayne revealed!

Demon

When Raven revived Damian in Apokalypse War, she knew that Damian would no longer be a normal human and so did he... And it would be permanent.

Sadly, she didn't recall reviving him due to the Flashpoint. Also, her revival had chained his soul to return to his body, which then healed thanks to her normal powers, and returned him to 'normal'.

His soul was still affected from that intervention.

Causing his past self of the same timeline to feel the sudden and strange aftereffects at barely 10 years old.

His vision got better, he could sense magic (he noticed this ability thanks to encountering a few who were using the magic arts and his new ability to understand their chanting), his body was inhumanly durable and stronger... He also got angry faster.
What he noticed lastly, was that when he was asleep, he found that his 'spirit', similar to a ghost, separated from his body and he could move through walls and stuff.

Needless to say he was confused and aggravated. When he was really angry his eyes glowed with a purple sheen, similar to Raven's normal eyes.

Even Raven noticed something was off with her magic. It felt like a foreign entity was bound to it from one moment to the next and she didn't know why or what.

Upon looking through her books, tomes and scrolls she found out what it was: a familiar.
She had gotten a familiar.
But she didn't know how it came to be, usually one created one with arbitrary objects, summoned one from hell or formed a blood contract with another being, making them technically one's servant. Raven had avoided making one as she didn't require one or wanted to involve anyone unless absolutely necessary.

But then, when Damian was forced to join the Teen Titans and made eyecontact with Raven he felt something. Something inside him stirred and he hurried to get away from the magic user.

He avoided joining them for any activity that entire day, too preoccupied by the unusual feeling in his chest, which felt both expanding and constricting at the same time, and a headache aspirin couldn't kill.

Then, around 2 hours later he heard a voice, a deep voice in his room. It wasn't his older brother, or anyone he met before, but he had a sense of familiarity with it. Then, after surveying the room for any hidden cam's or audio recording devices again, he realised something that made him tense and his scowl deepen:
The voice wasn't coming from anywhere in his room; It was in his head. Someone was mentally talking to him. And that voice had the audacity to say it was him from the future. When the voice continued, claiming it could explain his physical changes and help control them if he meditated he warily accepted.

10minutes into the exercise and a taller figure formed in his mind. They had the Robin suit, slightly larger with some alterations and a kryptonite-green sword strapped to their side. They took the mask off and he instantly knew through whatever connection of fate that this really was him. Their souls resonated as one and the same.
If he focused he could almost make out the heartbeat of their resonance. Alas, he made his older version talk, which first inquired about his current situation.
Giving the short recap his older version gave him the heads up of helping his teammates train as they will unavoidably face strong foes as one and needed to work together for them to win.

He then explained about Apokalypse, how the Justice League had failed, how he'd failed Grayson and Raven, his beloved, and how he had lead the League of Shadows. Then went to rescue his father, having died and been revived in the process thanks to Raven. Which is most likely the reason he even exists right now. He's a projection of Raven's magic on his soul.

The current pain in his chest was most likely his soul settling next to Damian's, thus inhabiting one body. If their intentions aligned it should lessen, the heart beating in the same rhythm.

Damian can call on him, he just needed to call his own name— mentally worked too.

In the morning he'd wake up drenched in sweat, still sitting in meditation and with his joints aching. He stretched them, feeling the ache settle. He called on his future self, both to make sure it hadn't been a foolish dream and to learn more about the team, now that he had a source of Intel.

It had not been a dream.
Neither the feeling of warmth and calmness when he was in the same room as Raven.
Neither had the warning of Blue Beetles attack been an illusion.

When Raven was healing him, she could sense him starting to heal the injury already, but then her mind was pulled away from further reading into his pain and memories. She saw an older boy, who's features aligned with Robin, standing in front of her. And she could feel it in the thrumming of her magic connecting with the boy. He was her familiar.

He introduced himself as Damian, but she could call him Beloved too.

He was apparently sharing Robin's body with his consent due to various circumstances which he can't get into detail at the moment. He warned her though: Trigon would be coming soon, he said, just before Robin's injury healed and she lost the connection with Damian.

She collapsed afterwards.