The names of the keys are a reference to FFVIII. Specifically, the sorceress's theme music, "Liberi Fatali."
The phrase that is repeated constantly in the song is "Fithos Lusec Wecos Vinosec." So, there you have it.
I clearly thought that was more well known than it actually is because you're not the first person to tell me they got stuck there.
Considering I'm deaf, no, the music means less than nothing to me.
I'd consider setting up an NPC that sings Liberi Fatali with that phrase.
No, Edge is not a playable character, so that wouldn't be an issue. I may include various nods to the Eblan Four, but they'll never really be in the spotlight.
That's fine, though the oldest one probably should be dead - just say 'I took over for Grandpa (name), when he died.'
Cuore is a bit more of a problem... Rydia HAS to be the last of the summoners. It is among the most essential plot points.
Maybe Cuore lost her power or something... I guess I can't just ignore it completely. I'll figure it out once the game gets up to the point where the player travels to Mist (which is part of the next chapter, so sooner rather than later).
Easy answer - a Maenad isn't a summoner - they had to basically 'steal' Rydia's Eidolons. With Rydia in full control of her summons and probably holding on to it, Curore can't access it unless Rydia wills it... and she probably didn't will it for -some- reason that might be useful to your story.
See (from the After Years wikia):
'The Maenads are powerful sorceresses able to teleport, use telekinesis, cast high-level Black Magic including Meteor, and summon Eidolons. Their capacity to summon Eidolons consists of petrifying their material forms and corrupting the Eidolon's mind, but Fusoya says this is not simply petrification, but a casting of the Eidolon's spirit into another dimension. This process can be disrupted by evoking an emotional response from the Eidolon. When this "awakening" occurs the Maenads lose the ability to summon that Eidolon. '