I did some math to find out which AP items were the best if you wanted as much damage as possible. I only did the math for Void staff, Horizon Focus, Shadowflame and Rabadon (considering you already have Luden and sorcerer boots).
In the end Horizon Focus is always higher if you can proc its effect. So I’m wondering why every Lux player for example aren’t buying it second item.
Because it procs on slows this season if you buy rylas before it you literally have the effect permantly active.
On dot champions that already like building rylas for the perma slow it’s very good synergy.
Next season however they are removing it being proced from slows so the rylas synergy is gone it will only work on 700+ range limiting it to artiely mages only which is fair since that item was meant for them and the rylas synergy is kinda dumb.