To prepare for the upcoming update at the end of November (presumably version 1.9), Fire Emblem Heroes will be offline for maintenance between 14th November at 11 pm (UTC) and 15th November at 2 am (UTC).
For reference, the downtime ends 1 hour and 30 mins before the next scheduled Feh Channel broadcast starts. So, with luck, it won’t be long before we know what’s in the mysterious planned update!
@FE_Heroes_JP has given us a peak at the next Grand Hero Battle featuring Arvis from Genealogy of the Holy War! Check out his map below:
Arvis comes equipped with his powerful Valflame tome, which includes a combination Atk/Res Ploy effect. He also has a unique B skill, Recover Ring, that restores 10 HP every turn. His remaining skills are Growing Flame and Def Ploy.
Arvis’s Grand Hero Battle is schedule to start tomorrow, 18 October, at 7:00am UTC. We’ll find out more details then!
Additionally, Fire Emblem Heroes will be undergoing extended maintenance soon. The game will be unavailable from 11:00pm UTC on 23 October through 2:00am UTC on 24 October.
To prepare for version 1.5.0 of Fire Emblem Heroes, the game will go offline between 26th June 2016 at 11 pm and 27th June 2016 at 1 am (UTC; times are approximate). No details about the contents of this update or its release date have been provided.
Additionally, while it was known to data-miners, the official Japanese Twitter has revealed that the Michalis Grand Hero Battle will be returning tomorrow. Presumably like other repeats, there will be related quests to earn more copies of Michalis.