Dark Royals Alpha/Omega AU
Mates, even those only acknowledged by one side, are capable of hurting each other much more deeply than the average person. In the case of Lucifer, this would translate to any damage at all.
Lucifer spent a good amount of time chasing Alastor down between rebuild days of the hotel following the S1 finale.
He let the sinner rebuff or dodge him for the most part, because the wound wasn't killing him yet.
He did get a bit of sneaky healing in when Alastor returned to the hotel and everyone hugged him.
At this point Charlie has some suspicions, the old hotel had a brief notation in the staff office from the time the royal family used the building as a summer estate.
"The princess was kept in accompaniment by a cervid sinner. Their majesties advised distance. All meals and requests are to go through them."
So she suspects Alastor might have been her nanny, but he left too early for her to remember him. Dad doesn't seem to hate him so he wasn't fired, but why did he leave then? Surely overlord status was less than a connection to the royal family.
Alastor's wound starts getting worse again and it shows. He's feverish, withdrawn, and quick to lash out now. Lucifer, having had enough, reveals that Alastor is injured and the other residents join in on applying pressure for him to let them help.
It isn't pretty, in the midst of wrestling the Radio Demon down, Alastor screams and claws, catching the King across the cheek and, to the shock of most, drawing blood.
It shocks everyone else, but not Lucifer, who knows he thinks of Alastor as his mate and just dismisses it as he wrestles down and forcibly heals Alastor - and as he does so Alastor starts flashback and begging him/'them' (Lucifer and Lilith) to stop.
Everyone else is horrified as they realise what this means, Charlie is staring as the puzzle pieces click into place - and Lucifer just happily ignores it as he heals Alastor who is feverishly trying to get away from him.
