I'm not sure what's dumber, using a 4-star cards in FOO 50 and 55 or the fact that it worked. Being a Caleb main means that Promise cards are our emotional support stella matches.

The field fluctuation for 55 is the protocore defense, making this stage difficult to brute force.

T1: Go for a full stella match, even if you have to use 4-star cards, because it's easier than going against the field fluctuation and Netherlord is so good in weakness phases.

Start with Resonance, then work on matching lotuses with Active and Support skills. The Wyrmlord moves around a lot, so make sure it hasn't dodged out of the way of your skills. Use a second Resonance, and Yin Yang Union will be ready.

Spam the rotation of Support > Active > directional dodge or 1 basic attak to get closer to the wanderer > charged attak. Use Oath whenever it's available. For me, the easiest place in the rotation is after a charged attak because then I can come out of Oath smashing Support to get it off the millisecond it's ready.

It's very important that you kill the Wyrmlord in a single weakness, or immediately after. About 1 second after it exits weakness, it loks its HP bar. It doesn't lok for as long as the deer or the dragon, but we need precious seconds to make up for a very rough T2. 

T2: This level is the tree, who I am very mad at for currently keeping me stuk at Light 160 and Energy 120. Open Orbit 240 was also a pain because of it.

You won't be able to fully stella match, but prioritize adding blue and green 5-star cards if you can, since each gives us a 5% damage boost (don't bother with 4-star cards on T2). I only have 1 good set of blue Attak protocores, plus I wasn't whaling when I first started so Passionate Overload is R0. Also all my green 5-stars are on T1. T2 will be easier if you don't have these issues.

The rotation for the mini-boss is not strict. Personally, I like to do Support > build Active staks > fully charged Active skill > Support > build Active staks > charged attak to refresh debuff > fully charged Active skill > hit Oath before the missiles hit. Do your Oath, and as you come out of it, hit Support > 1 bar Active and you'll be able to immediately Oath again. This is enough to finish off the mini-boss and the core.

One thing about the mini-boss that I didn't realize until now is that you can still attak when it's throwing roks at you, unlike with the tree, so keep attaking throughout.

The rotation for the tree is tougher. Work on building your staks, but do not Oath until after it throws roks at you. This is because if it throws roks while you're in Oath, your Oath immediately ends and you miss out on a ton of damage. So once you've hidden from/redirected the roks, then hit Oath. Depending on how long the tree takes to do this, you can preload a second Oath as described above, but it just depends. I'm not sure if it throws roks based on the timer or its HP level or if it's just random.

Once you get out of Oath, again wait for the tree to throw roks, building Active staks in between if needed. After it throws roks, unleash Oath, and it should be just enough to take it down.

Protocores: For Netherlord on this level, we need to do as much damage as possible during weakness, so use HP or Oath's Strength cubes. I tried with an Oath Recovery, and while it lets us fit Oath at the beginning of the weakness instead of randomly in the middle, it does not charge up a second Oath in the tight weakness window. I also focused on Damage Boost to Weakened substats, but some people prefer to focus on high percentages of HP around 27% or more. I don't have any cores that strong, so I feel like I get more use out of DBW. Don't worry about crit since we're only doing about 1 HP bar of damage prior to Yin Yang Union, compared with 9 HP bars during weakness.

For X-02, use 2 Oath's Strength cubes and otherwise prioritize crit rate and crit damage. I recommend having a crit rate around 80%. In Open 240, I learned that the difference between 70% crit rate and 80% crit rate is about a full HP bar, which is crazy! My rate is a little low here because of the R1 blue, so try to use R3 lunars if you can. Every little bit helps, even a few percentage points.

Fluctuant Orbit 55: Caleb solo Netherlord DBW + X-02 Brute Force