Marth

Fury 3 helps him lose HP then recovers with renewal 3(in his falchion) and use reciprocal aid to heal and ally.

Falchion (REFINE) His refine helps him buff allies within 2 spaces 2+ in each stat which makes him into a good healing bot and buff bot which makes him a good support unit

Just because he is a good buff/heal bot those not mean he can't be used offensively. Because his offensive stats are pretty good of 54/38 with fury 3.

Drag back helps so that if he defeats a enemy he can gets out of the range of any enemy but it can also be used to drag a enemy back and then have a ally to finish off the enemy

Close Def 3 Seal helps him survive against physical attacks but also attacks from dragons if he is attacked by any dragon and then he can finish off the enemy taking less damage then usual.

Drive Skills depending on the team i use Drive Spd/Atk/Def/Res helps him boost one stat depending on the team i use.

With Falcion +Res and Res 3 seal, Marth is becoming a threat to mages. He can currently surrive all mages. He also has Fury 3, Renewal 3, Breath of Life, Poison Strike (seal), Ardent Sacrifice and Aether for TT.

Dragon Supporter (Arena Defense) - CHEAP & EASY!

Preferred Boon - Speed
Preferred Bane - Res

With Marth's Falchion refine, he becomes a walking buff machine of +2Atk/+2Spd/+5Def/+5Res with this build. This makes him quite useful in arena defense, particularly when paired with other Infantry units who are more likely to stay near his 2-space buff radius. The buffs are unaffected by Panic Ploy which is also useful. While one could argue that an additional emblem buff would be better than Marth, he has the advantage of being fairly non-threatening if set as a defense team leader. He is particularly useful if your other 3 units are high merge, since his buffs improve them even further for little investment. His Falchion and high speed are also a legitimate threat against any dragon units, which are quite common in arena. Lastly, he is better than a dancer if your whole team is an enemy-phase team, since you do not want your units to be attacking first.

Fury 3 is a solid skill focused on keeping Marth alive for at least one hit. The +3 Speed from Fury is quite noteworthy on Marth's 34 (37 with boon) Speed stat, so there is little reason to take much else in the A slot.

Drag Back is the perfect option for messing with people in arena. It will move the enemy one space closer to your allies, and pull Marth back into the team so he can keep his buffs active. Even if Marth is horribly murdered from attacking an Effie, he will still pull her towards the team after he dies, which is a key advantage to this skill in the hands of the AI.

Dual defensive drives in the C and S slots are essential for turning enemy-phase dragons into unkillable monsters.

Rally Def Res is very important, because the AI will use this instead of suiciding into a blue unit, if a blue unit comes into range of Marth and Marth has an ally nearby.

The special on Marth does not matter, but we take Moonbow to help him get cheese kills when attacking thanks to his decent Speed, and to put a dent in armored foes. This will make him even more dangerous against dragons, who are very slow and will get doubled.

+ATK/-RES Marth +2 merge:

Pretty standard Falchion user build but with emphasis on ally support thanks to Marth's special refinement, which grants +2 Atk/Spd/Def/Res to allies within 2 spaces.

With the special refinement + Rally Def/Res + Drive Res 2 (C-skill) + Drive Def 2 (seal), Marth can potentially boost an ally's def/res by a whopping 8.

This is a great enemy phase support build and can work on a number of mixed teams.

If a Drive Spd or Atk seal ever comes out, you could opt for a more offensive minded overdrive support.

This is shown as Marth's optimal build, and I agree with that. However, I'm going to give my thoughts on why I think so, and any alternative skills you can use.

First off, I personally don't use Marth as a buffbot, and prefer that the hero king stands as a solid unit on his own combat wise as well. He has a well-rounded stat spread, so specializing him for something such as a strictly offensive build with life and death as opposed to an all-rounder support hybrid is sort of a waste in my opinion, as he will have to sacrafice his high defense and average resistance for offensive capabilities, when fury could round his stats better.

Ivs: +Spd, -Res/Hp- Getting to the build, +spd -res are chosen for his ivs as his speed is already fairly high, allowing him to ensure more doubles and to avoid receiving them. His resistance is around average, sitting at 23, so losing 3 shouldn't affect him much. -hp may also be chosen, as the damage he takes from mages and dragons will be reduced by 3 points, however it should be noted that he takes -4 in this stat with a bane, so -res is generally better.

Weapon: Falchion (+Eff)- His unique refine doesn't do too much for him as a combat unit, which is why people overlooked it at first. However, it gives him +3 hp, renewal 3, and a drive spectrum skill that provides +2 atk/spd/def/res to all allies within 2 spaces of him. This is very useful, and also means that his renewal will be more reliable and he can switch hp with allies using reciprocal aid or share 10hp with ardent sacrifice, and gain it back easier.

Assist: Reciprocal Aid/Ardent Sacrifice/Any Double Rally- Going back a bit to him having reciprocal aid or ardent sacrafice, having renewal 3 helps him better manage his hp gain, with the former letting him switch around hp as needed in case he or another ally needs to have more hp to ensure they can safely engage in combat, and the latter letting him give small amounts of hp to an ally and regaining it back with renewal 3 from his weapon. A double rally skill may also be used to increase arena score and further increase his buffing potential.

Special: Luna/Moonbow/Aether- Luna is highly recommended as he will probably do well against greens, and this skill can ensure victory over green or red physical units with high defense, or KOing a dangerous ranged unit that could pose as a threat to him or your team, as Luna should be ready after a single round of combat, assuming said round is 3 turns long. Moonbow can be taken to help him finish off units with higher defenses or deal more damage to them in a single round, assuming he doubles. And finally, aether can be taken to both increase arena score, and to let him deal a high amount of damage and heal back what hp he's lost.

A: Distant Counter- A lot of people may be unsure of putting this skill on Marth, however he poses as a surprisingly good candidate of the skill. While many sword units with distant counter weapons exist, Marth has good defense, decent resistance, and enough speed to avoid many doubles, making him a better all-rounder as he is able to defend himself against green and red mages (note: watch out for swordbreaker and doubles from red mages) that he would normally want to stay back from on enemy phase, and even deal with non-brave archers (note: obviously excluding Brave Lyn), although they may be very uncommon in the arena.

B: Quick Riposte 3/Renewal 3/Swordbreaker 3- Quick Riposte is a great skill for most enemy phase units with distant counter, since many units in the arena are speedy and may survive a hit from the hero king, and possibly even retaliate with a lethal special. Since 37 speed isn't enough to double consistently, but enough to avoid a huge amount of units from doubling him, QR is a great skill to equip on Marth. Renewal 3 can be taken to restore 20 hp every 2 turns, which is insane, and helps his potential of regaining health and getting back into combat, or being a pseudo healer. Swordbreaker 3 can also be chosen due to popular speedy sword units in the arena such as Ayra and Mia, who may be able to take out the poor hero king out on enemy phase due to sheer offensive power and speed.

C: Drive Spd 3/Drive Atk 3/Drive Def 3/Drive Res 3/Varies on Team- His C skill is self explanatory, it adds +3 to stack with one of the stats from his drive spectrum ability for increased support capability. This skill is up to the player's preference and team's needs.

Seal: Distant Defense 3- While 29 defense is solid, it could still be better, and 20-23 res (depending on ivs) is rather low. This seal adds +6 def/res when a ranged enemy attacks him, meaning he will have 35 defense and 26-29 res (depending on ivs) on enemy phase against ranged units. This is much better, and he will be able to handle most ranged units well, aside from blue mages and most, if not all, brave users.

This is my build for Marth, and my thoughts on it. For anyone who is looking to use the hero king, I hope this guide helps you in building him well. :)