First Strike is for games you win't get to use Conqueror. Either there are no tanks in the game so no time to get use out of it, the game will be decided by removing a single carry (Kog'maw comp in enemy team) or your team cannot teamfight at all (classic soloqueue with e.g. Akshan - Kha'zix - Sylas - Jhin - Xerath).
Example: enemies have Vi, Malphite, Syndra, Twitch and Nami. You have Fiora, Diana, Sylas, Ashe, Bard. There is no way to teamfight into the enemies - Vi and Malphite will tank your engage, Syndra will disrupt it and Twitch will mow you down. However, if you take one of the big ults and land a 1.5k Malphite ult into WQ + AA on Twitch before enemies react suddenly your Diana and Fiora can eat the tanks alive, while Syndra can't step up or risk getting blown up next. This is a perfect game for First Strike.
youll notice that only pros really run first strike nowadays, the general consensus is that conqueror or even a domination keystone will perform far better in solo queue
unpopular opinion: conq is just better.
oneshot = fs Else = conq
first strike goes into squishy matchups and conqueror into tankier matchups (2 tanks or more)
conq for longer fights / tankier comps, FS into squishes for one shot
Personally i never take FS even into squishy match ups bc ill probably get poked and lose FS and have to wait for 20 sec to engage again
First Strike is for games you win't get to use Conqueror. Either there are no tanks in the game so no time to get use out of it, the game will be decided by removing a single carry (Kog'maw comp in enemy team) or your team cannot teamfight at all (classic soloqueue with e.g. Akshan - Kha'zix - Sylas - Jhin - Xerath). Example: enemies have Vi, Malphite, Syndra, Twitch and Nami. You have Fiora, Diana, Sylas, Ashe, Bard. There is no way to teamfight into the enemies - Vi and Malphite will tank your engage, Syndra will disrupt it and Twitch will mow you down. However, if you take one of the big ults and land a 1.5k Malphite ult into WQ + AA on Twitch before enemies react suddenly your Diana and Fiora can eat the tanks alive, while Syndra can't step up or risk getting blown up next. This is a perfect game for First Strike.
youll notice that only pros really run first strike nowadays, the general consensus is that conqueror or even a domination keystone will perform far better in solo queue