She's great! I have a +Atk -Spd one, and just give her Death Blow with Desp and Brash Assault in the seal slot and she'll wreck house. Not to mention her phenomenal Resistance. Overall she's plain powerful, all you need is to try to make sure she won't get a big hit or a double from any physical units.
Honestly, to my surprise, I found her pretty lackluster as compared to other slow bulky mages (i.e. Lilina, Julia, etc). Mine has good IVs and is lightly merged, so it was quite a disappointment that she really doesn't stand up well in combat. I did build her as enemy phase unit so maybe she would do better as a player face with brash assault? Might have to try that.
I'm one of those people who love to use units just because they're special to you xD
Micaiah was my most hyped character since the release of the game (always voted for her in choose your legend), stocked tons of f2p orb to get her and I was really happy when she came out (just a little sad with her spd tbh xD)
I gotta say that she's not a must have unit, pretty decent vanilla kit, Sacrifice for pseudo healer and her tome is just that great -but she'll not change your gameplay drastically.
I like to have tons of skills on units that I use the most, so I have on her Darting/Killing Blow, L&D and a bunch of specials, she's a nuke!! Brash + desp with Sacrifice is really easy to use and will defeat almost anything, just beware to not let in pyshical danger. (If her def wasn't that bad I would use Close counter + Vantage just for the lulz :v)
I have one merged +2 (Spd boon/Res bane/L&D/Desp/Spd +3 seal) with 55Atk and 40 spd (Brash Assault seal is on LA Roy) even with L&D and Res bane she still got 31, sometimes I change her build depending on what I'll do with her :3
TL;DR - She's great! But if you're low on orbs and doesn't want her that badly I would say to skip it (specialy if you're f2p), otherwise just go for it! x3
I love using Micaiah, I have a +Atk, -Def one! Thani is amazing in my opinion, it one shots many armors and horse units. Soleil, Zelgius, Ayra, Hardin, Effie, all no problem! With DD as a sacred seal, she can tank one shot from B!Lyn or Reinhardt and then one shot them.
Actually I've used her to tank archers and projectiles... XD
I got a neutral one, I put on her the sacred seal dd3, stacked a hone defense, plus putting her beside her support ally (playing enemy phase) and she handles well a lot of stuff! 36 def & 49 res are plenty. Besides, Thani helps her tank horse riders and armors by 30% on the first hit, aaaand she kills them on retaliation because of its effect against them. Added a renewal 3 for survival.
Pokemon GO
Fire Emblem Heroes
Fate Grand Order
Dragonball Legends
Dragalia Lost
IV Calc
Heroes