Ok, SO. Cycnus was a son of Hyria (or Thyria, depending on how the name is spelled) and Apollo. He was a hunter who was described as conceited, a very Narcissus-type character. He had a ton of admirers because he was so dang pretty, and many young men would attempt to follow him in his hunting expeditions. However, he really just wanted to hunt alone and didn't really care about any of these people, so they eventually all left, except for one man. This man's name was Phylius, and most sources I've found say he was infatuated with Cycnus, if they were not just already in a relationship.
Now, Phylius refused to abandon Cycnus, no matter how much Cycnus shunned him, so Cycnus eventually gave him three tasks to prove himself. The first was to kill a lion that was terrorizing a nearby village without any weapons. Obviously, Cycnus did not want Phylius to succeed, and probably just wanted him to go away already. Phylius, however, took up the task, and killed the lion by: Eating a whole bunch of food and wine, throwing it back up, waiting for the lion to lick up that mess, and, once the lion was intoxicated, strangling it to death with his own shirt.
Now. I don't know about you. But if a man did that in front of me, I would run for the hills, because, and I cannot stress this enough, what the fuck. Cycnus was obviously not impressed, and gave Phylius a second task: Three man eating vultures were terrorizing the smae village (honestly, that poor village) so now Phylius had to catch them without weapons too. Phylius, master of fucked up solutions to these sorts of things, decided to cover himself in blood from a dead hare, wait for the vultures to come for him, grab them by their legs, and bodily drag them directly to Cycnus.
Let's recap. Cycnus has had to deal with this man following him despite him pretty clearly not wanting him there, had to watch him do whatever the fuck he did to the lion, and now he's standing in front of him covered in blood with three violent birds held by the ankle, all smiles and "these are for you!"
Restraining order. Immediately.
But those don't exist yet, so Cycnus gives him a third task. Go seperate a bull from it's herd and drag it all the way to the nearest temple of Zeus for sacrifice. And, side note, have you noticed that everything Cycnus has been asking Phylius to do has been acts of community service? Like, these aren't just fuck you fetch quests, That poor city has been saved from a near endless siege, and now Cycnus is giving his proper respects to Zeus. All of this bullshit, and Cycnus still manages to give back to the people. What a king.
Anyway, Phylius basically gives up at this point, but then, through what was probably divine intervention, a bull basically just collapses in front of him. He drags the thing to Zeus' temple, but then Heracles himself shows up. He tells Phylius that he doesn't have to listen to Cycnus anymore and he can like, leave. Maybe live his own life? Phylius agrees to this, and abandons the final task and Cycnus. Cycnus feels disgraced by this, probably because an actual god told Phylius to abandon him, with the implication that Phylius was too good for Cycnus, which like, no. Either way, he ended up throwing himself off of a cliff, which Apollo immediately disagreed with, turning him (and his mother, who had also thrown herself off the cliff, which like, goddamn) into the first swans.
The moral of the story seems to be not to take those who love you for granted. And like, fine, whatever, maybe I can see where that's coming from. But Cycnus never forced Phylius to stay by his side or do any of those tasks. Phylius was the one throwing himself at Cycnus while he literally just wanted to hunt alone. So I am 100% on Cycnus side and he did nothing wrong your honor.
If you read all the way through this, take this drawing I made of Cycnus a while ago, plus his half-brother Linos, who was also completely innocent but like, nobody disagrees with me on that so I don't have to defend him as much /j