|As Marth is a Falchion wielder, he can serve as both an effective healer and a fighter, or he could opt to improve his great offensive capabilities further.
Weapon: Falchion is Marth's weapon of choice. When given its special skill, it will grant him +4 to all stats if he has an ally next to him. This increases his bulk when defending against attacks, while improving his already great offensive stat spread. The Falchion will also restore 10 HP every other turn, improving his sustain, which is especially helpful in endurance styled modes. It can also help offset the self injury from Fury 3. Finally, it's effective against dragons, which means Marth can help strike down any opposing dragons the player faces.
Assist: Reciprocal Aid is what allows Marth to act as a healer of sorts, and is best used if he has Renewal 3 as well. With these skills, Marth will heal 20 HP every other turn, as well as 20 HP at the start of each map for endurance styled modes. He can then proceed to share his pool of HP with injured allies and have his skills heal back up the damages for himself. Should the player use Marth in other modes or feel like this is not necessary, then another Assist like Reposition can be used instead for its movement utility, helping Marth move his allies around instead.
Special: Glimmer is Marth's Special of choice, as it has a fast charge and helps him do even more damage. With Marth's good Spd, he should be able to double a lot of his opponents and activate it, potentially helping him secure the victory against his foe.
A Passive: Fury 3 is chosen as Marth's A skill. It improves his overall combat performance as it grants Marth +3 to all stats, although this comes at the cost of 6 HP after each round of combat. However, the self injury is offset by the Falchion's self recovery.
B Passive: Renewal 3 is an option for Marth's B skill if he wants to serve as a medic for his allies, and should only be chosen if his Assist is Reciprocal Aid. With it, he can heal even more HP, and it lines up with his Falchion's self recovery, letting Marth heal 20 HP every other turn, which he can then use to help heal his allies. However, should the player feel like this is not necessary, or use Marth in less drawn out game modes, then Swordbreaker 3 is a great option for him as his B skill. This instead lets him duel with opposing sword users and come out on top.
C Passive: Marth's C skill is flexible, open to be whatever the player needs. A buffing skill like a Drive or a Spur could work well to help him support his team, but this is up to the player's team composition and discretion.
Sacred Seal: Attack +3 is an option for Marth's Seal slot, as a simple attack boost is always nice. However, this skill slot flexible, open to be whatever the player needs, depending on the player's team composition and discretion.