This guide will be covering the difficult stages in Stalker Files, which are the Rita challenge missions.
Here is the full video demonstration:
Timestamps are as follows:
Stage 7: 0:38
Stage 8: 2:47
Stage 9: 5:57
Stage 10: 7:30
Umbral Rose: SS Rank Minimal. S Rank possible with great gear
Equipment: Azure Storm/Senescence or better, Picasso T, M, Reburn (Formals) T, M, Darwin B, or better (physical Gacha stigmatas)
Phantom Iron: S Rank Minimal. A Rank possible with great gear
Equipment: Carmine Steel or better, Theresa Origins or better (lightning Gacha stigmatas)
Artemis: Optional. She has a powerful leader skill and can provide additional off-field support (with Origins, Beethoven, or similar stigmatas) as needed, and a fully-kitted Artemis can make this a breeze.
I will not be covering the first 6 stages, since they are all much easier than these final stages. Strategies and loadouts I showed here can also be applied in earlier stages.
Note that while I used SSS Umbral Rose for my video demonstration, a SS-rank Umbral Rose is sufficient, since UR only gains about 6% more ATK and a fairly irrelevant skill on Rank up.
A fairly straightforward stage where you go up against the three cursed Himeko souls.
Umbral Rose's ultimate packs powerful AOE potentials, making timing their deaths a relatively easy task.
With this loadout, your ult can usually take out around 20% of the Himekos' HP, but only 10% on the Ice soul due to its high resistance. Plan their HP accordingly so they all die within the Soul Link window.
The enemy attacks are very punishing, though they're also clearly telegraphed (The Ice soul has the Himeko charge rings, Fire soul bubbles up before exploding, and while Lightning's attacks are far more unpredictable, she can be stunlocked by UR fairly easily). Focus on dodging as soon as any Himeko try to get close to you if you are having trouble staying alive, and DPS through using charged attacks and dodge time-fracture windows.
I recommend taking a Herrscher of the Void Friend Support here as this provides the greatest DPS increase. Alternatively, a highly ranked Lightning Empress support may help you get even a third ultimate out.
Due to type advantage, Umbral Rose makes a great DPS in this stage as well.
My strategy here is to force the Boss to go into Overdrive at around 2.5 bars remaining, which will subsequently prevent his next Overdrive from retaining the damage reduction.
Let Phantom Iron stay onfield while Heimdall is trashing everything in Overdrive to mitigate damage taken by Umbral Rose.
DPS should not be a major issue here as Heimdall does not have particularly high resistance and he should only have opportunity to Overdrive twice (the second time without any damage reduction). If you are having trouble staying alive, you can try switching between Umbral Rose and Phantom Iron if your Phantom Iron is well-geared.
I recommend taking a Herrscher of the Void Friend Support here as this provides the highest DPS increase.
This stage essentially forbids Umbral Rose from doing damage, so feel free to throw Roald (or Tesla M/B) on her to provide some backline buff.
Fortunately, it does provide a very high built-in Elemental buff. Combine this with the high 49% All damage multiplier you receive from this loadout (25% from Formals 2-set, 24% from Darwin B), even A-rank Phantom Iron will have no problem obliterating the enemies in no time.
The major challenge in this stage is to mitigate health loss. Zombies are usually highly-interruptible and their attacks are quite predictable, but this stage will punish you harshly if you ever got hit. Add that on top of the Steel Soul passive and you might just die from one single hit. As such, taking Seele 2-set or Monet 2-set will help prevent unnecessary health losses (the lack of actual offensive effects from Seele or similar mitigation stigmatas are still acceptable since you have a powerful stage buff).
I recommend taking a Shadow Knight Friend Support to provide for an early ultimate and high elemental buff. Alternatively, Phantom Iron, Divine Prayer, Lightning Empress or Artemis (especially if you also have an Artemis) could also be powerful friend picks.
Oh boy. Here we are. The stage that collected many salty tears from captains around the globe.
Unfortunately, there is no real "trick" to this stage. Fortunately, it is still possible (albeit with a tight window) to clear without involving any gacha gear.
Pace yourself so that you have about 3 minutes to deal with Baldur, and 2 minutes to deal with Bronya. (This is especially true if your Umbral Rose is more geared than Phantom Iron)
A potentially stronger gear choice on Phantom Iron is Darwin T and Formals M/B, providing a stronger, more persistent buff compared to the more intermittent buff from Theresa Origins. However, Origins does allow for more frequent Carmine Steel activations, which improves sustain. (If you have Gene Reaper and Monet/Caravaggio sets, just run those since they provide vastly more damage)
I recommend taking a Snowy Sniper Friend Support here as getting dodges off is very essential in this stage, and both Umbral Rose and Phantom Iron have powerful dodge skills. Shadow Knight is also a decent pick, providing extra damage against Baldur.