|As the Mage Flier with highest Resistance, Morgan's ability to utilize ploys paired with superior movement as a flier should be taken seriously. This build looks to maximize on one of the many ways she can be lethal on the battlefield. Preferably, she should be +Res to maximize ploy potential, but she can also be +Atk or +Spd if you feel that she needs a little more killing potential.
First up in her skillset is her weapon. This one's a no-brainer. As a player phase build, Blarblade+ is great due to the utilization of buffs, especially nowadays with the Tactic skills being highly present in the metagame allowing her to perform well on both mixed and flier (due to Hone and Fortify Fliers) teams.
Her assists should help her move her or her allies around, which Reposition and Draw Back serve the best for.
Her specials make use of her high Resistance, both Iceberg and Glacies deal a lot of extra damage when activated. It's up to you, the player, whether you're willing to wait an extra turn for the higher Glacies damage or to have the quicker cooldowns at the cost of more damage with Iceberg.
Her A special is Swift Sparrow 2, increasing her attack power massively while not dropping her Resistance with Life and Death. Alternatively, she can run Death Blow 3, Darting Blow 3, and Mirror Strike 2, since they are all pretty good options for her, since they all help to make her faster or stronger against mages.
Her B special is Chill Spd 3, in order to maximize her ability to debuff opponents. If you're on a budget, you can also use B Tomebreaker 3 in order to gain an edge over high Res blue mages such as Linde and Delthea, or Lancebreaker 3 to guarantee the kills on lance units. Swordbreaker 3 and R Tomebreaker 3 are not recommended since Blarblade and the weapon triangle advantage already make her deal enough damage to likely kill reds in one shot.
Her C special is Res Ploy 3, used to lower enemy's defenses against her attacks. She can also run Spd Ploy 3 in order to allow for more doubles, though it won't stack with Chill Spd 3.
Her seal is Atk Ploy 3, used to lower enemy's offense. She can also run Def Ploy 3 in order to set the enemy up for a teammate to kill.
And that concludes her build. A ploy machine with strong 34/30 offense and a base 33 of resistance has the stats that allow her to be a strong mage killer. I hope you enjoy this build and thanks for reading :)