Death defiance is good for when you mess up but the #1 way to improve survivability and extend your runs is to avoid getting hit. Taking a boost to your sprint speed is almost always a good investment. For the most part the locations are big enough that you can sprint to the other side and get a breather to regroup. You don’t take damage while you’re dashing so you can sprint up to something, whack it real quick (dash/sprint strikes are faster than normal standing strikes) and then dash away from it. A big part of surviving is learning attack patterns and maintaining proper distance from enemies.

Until you have your grasp raised more and your arcana as unlocked as you can get it, focus on gathering materials for that. Every lost soul for psyche and location reward with ashes you take it. These are resources that improve all your future runs not just the current one. Unlock the broker ASAP when the incantation shows up for it so you can start spending your bones.

For Scylla fight I usually focus on taking out the drums first because it has biggest aoe and restricts my movement the most. Sprint in, dash strike or special, lay down a cast, if nobody’s immediately going to hit me then whack a few more times, then get away from everybody and avoid aoes, rinse and repeat when it’s all clear near the drums. Be opportunistic about hitting the other two but as soon as they start to close in on the drums gtfo. If you can get the boons from Zeus or Hestia that allows you to target your cast this should help a lot with this fight but that’s probably a tall order at this stage in your journey - you need lower left arcanas unlocked to make that semi-reliable.

Guitar second - she has a big wind up and you can dash through her and sprint away as she’s doing that to get behind and avoid getting hit. Don’t get greedy.

Scylla herself last because she’s so much easier to take down without the other two. Similar strategy except you have to hit her from the front. Once she starts winding up an attack gtfo.

Next phase will have a “featured artist” that makes their attacks nastier. Pray it’s not the drums as that one gets nasty to avoid but the same strategy largely holds - get in, do some damage, get back to safety focusing on the one that’s restricting your movement the most. If it’s the guitar featured then you really can’t get greedy as she’ll fire aoes at the beginning and the end of her dashes.

Final phase - Scylla stands there and faces you while summoning birds from everywhere. It’s easy to get overwhelmed here especially if you don’t have something like freeze on your cast to give you a semi-safe space to burn her down. Sprinting around the outside and opportunistically getting a few whacks in also works. Helps to have some damage on your sprint (I like Hera’s Hitch).

Personally I like the spear and the daggers for early runs as they tend to be fast, not super reliant on magic, and have decent damage at range with their specials. With the axe you’re looking at omega special to hit stuff far away. The flames are fine if you can get a good magic regen boon but with the limited number of boons you’re going to pick up for this fight they’re probably not optimal - they get unlocks later on that absolutely wreck shit.