45 years ago - Malcolm Merlyn is born.
41 years ago - 4-year-old Merlyn begins practicing archery.
27 years ago - 18-year-old Merlyn becomes a performer, known for his unerring skill with a bow.
22 years ago - 23-year-old Merlyn takes his first contract kill, quickly becoming one of the world's greatest assassins.
18 years ago - 27-year-old Merlyn immediately wants to challenge Green Arrow upon his debut, but waits because he doesn't want to jeopardize his bid to join the League of Assassins.
16 years ago - 29-year-old Merlyn challenges Green Arrow to a contest and beats him before killing a prominent politician in Star City to earn his place in the League of Assassins. severely beating Oliver in the process.
12 years ago - 33-year-old Merlyn murders Jack Kane for the League of Assassins.
6 years ago - 39-year-old Merlyn taunts Oliver Queen before taking a job to kill Bruce Wayne. Ollie stops him, proving he's become the better archer. Merlyn is recruited by Amanda Waller for the Suicide Squad.
5 years ago - 40-year-old Merlyn escapes the Suicide Squad after Rick Flagg's death. He returns to the League of Assassins, but is forced into a lower caste after his failed job.
2 years ago - 43-year-old Merlyn is sent to kill a target in Star City to earn his place in the League again. He succeeds, but only after being severely beaten by Connor Hawke.
Merlyn is a pretty proto-typical arch-nemesis villain for Green Arrow: He's essentially just the negative reflection of the same powers and skills as the hero he's meant to oppose. The fact that he also has the same weirdo beard as Oliver Queen is... well it's interesting, to say the least.
While he's had a little bit of traction in the wider DC universe, most notably during Identity Crisis, his largest profile appearance is unquestionably in the live action series Arrow, where he's one of the few villains that has maintained an almost consistent presence on the show since it began, and is played by perennial genre superstar John Barrowman. We didn't completely ape Barrowman's Merlyn; we've kept him as an Assassin and member of the League of Assassins, rather than ever making him a businessman in Star City or having taken over the League after the death or Ra's Al Ghul (spoilers? I guess?), But we did take one idea directly from the show, and thatr's his name. In the comics, Merlyn the Magician is a stage name. His actual name is Arthur King, which... doesn't really make sense, does it? Especially in a timeline where Merlin was an actual person. SO we've adapted the name used in the TV series.
Merlyn actually creates a pretty cool window into the functioning of the members of the League of Assassins. they're often depicted as faceless ninjas, but Merlyn is very much his own person. We get to see just what it's like to be one of the world's elite assassins who is actively trying to earn his place within the League. WE also, obviously, included him in our initial Suicide Squad, just because he happens to be such a good fit.