Chrom

Weapon: Sealed Falchion (+Eff)

Assist: Positional Assist  / Flexible

Special: Noontime / Sol

Passive A: Distant Counter

Passive B: Spurn / Repel / Close Call

Passive C: Joint Drive Spd / Spd Smoke / Flexible

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

• This build retains Chrom’s typical defensive playstyle, but instead aims to do so through Speed-stacking to leverage damage reduction-based skills like Spurn. His initially unimpressive base Speed may make this seem unwieldy, but his access to numerous Speed boosts — such as from his four-point +SPD IV, Blessings, and Sealed Falchion — does certainly make this a possibility. 
  • That being said, for Chrom to truly shine and be effective with this set, heavy investment will be necessary. This means incorporating a mix of high merges, Summoner Support, Dragonflowers, and his Resplendent if available alongside support from his allies. 
• The success of this build lies in the usage of a Speed-based reduction skill in Chrom’s B slot, which directly decrease the amount of damage he takes from opposing foes (up to a maximum of 40%) based on how much faster he is; this makes any available Speed boost well appreciated. Of those available, Spurn is generally ideal as it also aids his damage, but Repel or Close Call nonetheless remain useful if Spurn is unavailable.
• Combining this reduction with Distant Counter and healing Specials help him maximize his versatility, expanding the breadth of foes he can handle effectively while providing ample sustain to supplement his tanking. If accelerated cooldown support from Brave Lucina’s refined Geirskögul or New Year Velouria’s Renewed Fang is available, Noontime is preferred for instant activations on each counterattack. Otherwise, Sol should be used.
• For his C slot, Joint Drive Spd is a stellar option to build upon the Exalted Prince’s Speed further and solidify his performance across the board. Spd Smoke is a more readily available alternative that serves a similar purpose, but comes with the drawback of needing Chrom to engage in combat at least once first to reap benefits. 
• Lastly, any Sacred Seal that enhances Chrom’s Speed can realistically be used here, though Solo skills are the best available for their dual phase functionality and high overall boosts. His innate damage output is typically strong enough such that Spd/Res Solo is preferred to try to patch up his magical bulk, but Atk/Spd Solo works well regardless.

Preferred IV: +ATK or +RES / -HP

Weapon: Sealed Falchion (+Eff)

Assist: Positional Assist / Flexible

Special: Noontime / Sol

Passive A: Distant Counter 

Passive B: Null C-Disrupt / Special Spiral / Null Follow-Up / Lull Atk/Def

Passive C: Joint Drive Atk / Pulse Smoke / Def Smoke / Flexible

Sacred Seal: Quick Riposte / Mirror Stance / Atk/Def Solo / Fierce Stance / Mystic Boost

• This build instead capitalizes on Chrom’s innate statline and the widespread improvements granted by his refined Sealed Falchion to perform admirably as more of a generalist. A +ATK IV is Chrom’s ideal choice for boosted damage and effectiveness at using healing Specials, though the ubiquity of magic threats in Aether Raids makes +RES potentially worthwhile as well.
• Distant Counter once again remains Chrom’s preferred A skill for maximum versatility, and healing Specials are recommended to further boost his longevity. The choice between Noontime and Sol depends on whether he has access to accelerated cooldown support (such as from Brave Lucina).
• Meanwhile, his B skill options are diverse and depend on skill availability and the type of utility one prefers:
  • Null C-Disrupt stands out amongst other candidates to shut down the common threats of Dazzling Staff healers and/or Firesweep weapons — the likes of which can easily cripple him through their counterattack-negating ability. 
  • Special Spiral works excellently for more one-shot oriented playstyles and allow for instant Sol activations on Chrom’s first counterattack every round of combat; this serves to maximize the amount of HP he can heal. 
  • Although Sealed Falchion’s follow-up negation effect does help counter foes that rely on automatic doubles, Null Follow-Up remains an stellar B skill to instead guarantee Chrom’s ability to work around Impact effects if using the Quick Riposte seal. 
  • Lastly, Lull Atk/Def is another option to further improve Chrom’s bulk and damage. It also allows him to break through enemy bonuses, though this may not be particularly valuable in AR-O given the lack of visible buffs in Defense teams.
• Joint Drive Atk is a fantastic choice to heighten Chrom’s damage even further, secure more KOs and greater healing from Sol/Noontime. If Infantry Pulse teams are a common threat in your Offense runs, Pulse Smoke should be considered to effectively shut them down. Regular stat-targeting Smoke skills work well for general purposes as well. 
• The Quick Riposte Sacred Seal grants Chrom some wiggle room and makes him less dependent on OHKOing foes by providing an automatic follow-up in the Enemy Phase. Alternatively, Mystic Boost imparts additional healing and anti-magic capabilities, thus lending itself well to this playstyle, or standard stat-boosting seals may be used.