Fjorm

Preferred IV: +ATK or +RES or +SPD

Weapon: Leiptr (+EFF)

Assist: Positional Assist / Flexible

Special: Ice Mirror II  

Passive A: Mirror Stance / Atk/Res Solo / Distant Def / Atk/Spd Solo / Breath Skills 

Passive B: Null C-Disrupt / Shield Pulse / Mystic Boost / Null Follow-Up / Lull Atk/Def 

Passive C: Smoke Skills / Joint Drive Skills / Time’s Pulse / Flexible

Sacred Seal: Quick Riposte / Mystic Boost / Distant Def / Spd/Res Solo / Mirror Stance

• The Princess of Ice shines defensively thanks to the combined power of her refined Leiptr and improved Ice Mirror II, though she proves particularly potent against ranged threats. Her balanced statline lets her realistically make good use of any Asset (barring +HP), but +ATK should be prioritized first to enhance her raw damage output and then +RES or +SPD if possible.
• Her upgraded Ice Mirror II is the prime Special to utilize here, imparting great anti-ranged capabilities (who are typically the most pressing threats in enemy teams) with its concurrent survivability and damage boost against them. 
• To ensure she can consistently maintain its effects, Fjorm should ideally be provided with some form of Breath-esque effect to activate it on every counterattack, such as through certain support units (like Brave Lucina or Summer Hilda) or simply a Breath of choice in her A slot. Other options include using Time’s Pulse or her base Shield Pulse. 
• Since Leiptr already comes packed with what would be Fjorm’s ideal A skill, she has the ability to take standard stat-boosting A skills instead to further enhance her performance. 
  • Mirror Stance is a stellar choice to build upon her two primary stats and slow down enemy Special activations via an innate Guard effect. This is especially helpful against foes with automatic doubles if she’s not equipped with Null Follow-Up, since one of the main threats in tanking such foes without shutting down their follow-up effects is letting them quickly access their Special.
  • Alternatively, Solo skills may be used for their dual phase functionality and potent stat augmentations, or Distant Def to fully invest into her ranged bulk at the cost of her damage (and with its fourth-tier version, she can deny visible buffs too!)
  • As a side note, contrary to what her base kit may implay, do not use Unity skills in her A skill; her refined Leiptr neutralizes any penalties she has, so all such skills would do is provide a +5 stat boost and nothing further. 
• Her B skill is fairly flexible as well. Beyond her base Shield Pulse for immediate access to Ice Mirror II (on top of supplemental damage reduction), Fjorm can also equip Null C-Disrupt to counter Dazzling Staff and Firesweep Bow wielders, Mystic Boost to gain constant healing, Null Follow-Up to counter foes with automatic follow-up attacks (e.g. Valentine’s Lif, Micaiah, Bramimond, etc.), or a Lull skill for further stat advantages. 
• Although Fjorm isn’t attached to any specific C skill, good candidates include Smoke skills and Joint Drive skills. Of the Smoke skills currently available, Pulse Smoke is recommended if aiming to use the ice princess in Aether Raids Offense if Infantry Pulse compositions are a particular issue; otherwise, Def Smoke and Atk Smoke provide more general applicability. Time’s Pulse is also an option to ensure Ice Mirror’s activation on Fjorm’s counterattack without needing a Breath effect. 
• The Quick Riposte Sacred Seal works excellently to ensure Fjorm’s follow-up attack in the Enemy Phase, as her Speed will usually be enough to only deny enemy doubles outside of support-intensive situations. If unavailable, the Mystic Boost Sacred Seal helps grant Fjorm further longevity through healing, or any stat-enhancing seal that targets her key stats can work too.

Weapon: Leiptr (+EFF)

Assist: Positional Assist / Flexible

Special: Ice Mirror II 

Passive A: Swift Stance / Atk/Spd Solo / Kestrel Stance / Spd/Res Solo

Passive B: Spurn / Repel / Close Call

Passive C: Joint Drive Spd / Smoke Skills / Joint Drive Skills / Flexible

Sacred Seal: Atk/Spd Solo / Spd/Res Solo 

• Although this build once again emphasizes Fjorm’s capacity for tanking, it instead hinges her performance on Speed-stacking to exploit the effects of damage reduction skills like Spurn. Her mediocre base Speed of 31 may make this appear underwhelming, but her access to a +4 Speed boost, penalty neutralization, and free A skill access from refined Leiptr — alongside appropriate ally support, investment, and IV selection — does let her make surprisingly solid use of such an approach. 
• Naturally, the most important aspect of this set is Fjorm’s B slot as her success here rests largely on the usage of a Speed-based reduction skill, potentially mitigating up to a maximum of 40% damage depending on how much faster she is than her opponent. Coupled with Ice Mirror’s own damage reduction against ranged (though do note that these will be multiplicative and not additive), Fjorm can shrug off considerable damage as long as she can obtain sufficient Speed boosts.
  • Spurn is the most generally useful of those available for its complementary damage boost, helping offset her middling Attack value. However, if unavailable, Repel and Close Call are still very much useful options — they just won't provide much functionality outside of their damage reduction effects.
• Fjorm’s A skill should ideally be something that enhances her Speed, and then one of her Attack or Resistance stats; the choice here depends on whether one prefers greater damage or stronger durability. Stance 4 skills are incredibly useful against foes with inbuilt follow-up mechanics, preventing their Special activations through a handy Guard effect. For pure stats, a Solo skill should be equipped. 
• Joint Drive Spd is a standout C skill option to further augment Fjorm’s Speed and grant some ally support on the side, though Spd Smoke may also be considered for a more readily available alternative at the cost of not doing anything in her first round of combat. 
• For her Sacred Seal, Fjorm unsurprisingly prefers anything that enhances her Speed, though Solo skills are likely ideal for their strong stat enhancements and dual phase functionality. Atk/Spd Solo and Spd/Res Solo are both excellent — picking between them again comes down to whether tanking or damage potential is preferred, but you can’t go wrong with either.