Defeating Quist is a natural story progression boss battle. You can’t miss it along the way, however you can play it too soon and make it frustrating for yourself. Be sure to first defeat the AI boss, ROXY, so that Quist’s tower does not have her lockdown in effect, making the platforming much easier. In some cases, it’s even impossible to scale Quist’s tower if your agility is too low and you've not yet defeated ROXY.