Resplendent Serra will be available in Fire Emblem Heroes until November 24, 2021, with Resplendent Ryoma following between November 24, 2021 until December 9, 2021.
Ryoma is going to be Resplendent soon, as Nintendo announced he’ll be the next hero to get that treatment in Fire Emblem Heroes.
The current Fire Emblem Heroes Resplendent Hero is Serra.
Fire Emblem Heroes is available for Android and Apple iOS devices.