SPOILER WARNING: This article contains major spoilers for "Sins of the Father," the latest episode of "Arrow."
At the end of "Unchained," last week's episode of "Arrow," Nyssa al Ghul offered Oliver Queen a deal: a cure for Thea's blood lust in exchange for Malcolm Merlyn's death. While things didn't exactly go as planned in "Sins of the Father," the end result was the same, and she ended up as Ra's al Ghul thanks to Oliver's machinations -- just before she disbanded the League of Assassins for good, anyway.
Oliver went into the episode determined to find a diplomatic solution to the war between Nyssa and Merlyn's factions, which would have worked just fine if Merlyn had gone along with it. After Merlyn refused to give up his position, Oliver arranged a battle between Nyssa and the current Ra's al Ghul, before stepping in on Nyssa's behalf. Oliver easily defeated Merlyn and chopped Merlyn's left hand off in the process, allowing leadership of the League to fall to Nyssa. Nyssa then filled her end of the bargain and offered Oliver the Lotus, which effectively cured Thea.
However, Nyssa had other plans and disbanded the League of Assassins for good. Earlier in the episode, Laurel had a heart-to-heart with her; she begged Nyssa to step out from underneath her father's shadow. Nyssa does just that, symbolically melting the ring of the Demon's Head in front of Merlyn, Oliver and Laurel before washing her hands of the League. Furious, Merlyn stormed out of the room, but not before promising Oliver a fate worse than death.
At the close of the episode, Merlyn makes good on his threats and meets up with Damien Darhk, revealing a crucial piece of information about Oliver's life: he has a son named William. After Darhk's attack on Felicity, the future doesn't look so bright for Oliver's secret child.
Oliver isn't the only one with familial trouble. Felicity tried to make peace between herself and her father, a.k.a. the Calculator. However, after discovering he tried to steal tech from Palmer Technologies during a visit she orchestrated, she had him arrested.