Most of them are easy to unlock.
Others have a bit more to do.
Nightmare Echo bosses do not award Ascension materials, nor can you spend Waveplates after you beat them.
You do get a first-time reward for defeating them, however.
Nightmare Echoes follow the same respawn timer rules as standard Overlord bosses.
Once defeated the first time, they’ll reappear after 30 seconds or so.
Also, like regular bosses, they have no deterministic way to farm for specific stats.
You just need to get lucky.
Unlocking the last two Nightmare Echoes takes a bit more doing.
Earning access to it isa three-step process.
The stele challenges requirestandingin a specific location around an altar to fill a progress value.
The final step to unlock the Nightmare: Tempest Mephis isencountering Fagaceae Peninsula’s four Dream Patrol challenges.
You donotneed to actually complete them to unlock the Mephis.
Specifically, you need tostart by heading to some ruins in the northwestern portion of Penitent’s Rest.
You’ll get some short dialog from an unknown voice, starting the Quest of Faith sidequest.
The quest requires you tohead to four ruins surrounding the mountainand defeat the enemies there.
Additionally, each arena has a number of torches in it.
Mourning Aix
Eternal Radiance
12% Fusion Damage bonus when equipped as a character’s primary Echo.
Impermanence Heron
Midnight Void
12% Havoc Damage bonus and 12% Heavy Attack Damage bonus.
Crownless
Havoc Clipse
12% Havoc Damage bonus and 12% Basic Attack Damage bonus.
