Quote Originally Posted by Jandor View Post
How does having the option of one, two, three, etc in reserve make any difference? Are the currently unsummoned ones always draining our aether to a small degree? Titan-egi just forever sat in our soul like a big orange aether capping dead weight?
I don't believe the option does, more so than the strength of the Egi itself.

Like, we couldn't get Ramuh-Egi, not because we already learned how to summon Ifrit/Titan/Garuda, but because Ramuh-Egi is simply more powerful than either of those 3 and thus needs a larger amount of aether to summon and us, even being the WoL, don't have enough (Or at least, didn't at the time)

Quote Originally Posted by Jandor View Post
I can't really remember, it's been a while. I was basically under the impression that all the Bahamut related stuff is using external sources of aether, specifically aether that Bahamut left a mark on, which in Eorzea at least is pretty much all of it to some degree or another.
Well, Dreadwyrm Trance is merely changing how the aether is used. Basically, instead of directing it into created entity, such as an Egi, it is instead turned inwardly to enhance yourself. (I assume this is how Ysayle was able to become Shiva without the need of a bunch of crystals like typical Primal summons, directing the aether inwards being vastly more efficient)

As noted by Y'mhitra:

"Rather than attempt to summon a separate, physical manifestation of certain egi, the most accomplished mages discovered that far less aether was required to infuse themselves with the essence of a primal's power."

Why Bahamut's aether? Because apparently Y'mhitra believes in "Go big or go home" (That and we had to face down an Ascian...). It also is somewhat convenient due to how much of Eorzea was splashed with his Aether during the Calamity so we didn't have to battle him to be able to use it (We just needed to go to the Cartineau Flats where it was "Steeped in Bahamut's energies" to initiate the Trance)

But yeah... Apparently, making a summon is not particularly efficient use of aether.

Though, with Demi-Bahamut, we literally get no lore about how we can summon it.

Literally all that is stated is:

PRINCIPIA
An unexpected development which you handled with exceptional grace, Mistress. And now, at long last, I can finally bequeath to you the highest secrets of summoning! Pray step forward!

YMHITRA
What a momentous occasion! The wisdom of the last of Allag's master summoners is yours!

Like... Great. But how?

How do I now randomly have the ability to summon Demi-Bahamut when previously I couldn't even manage a simple Ramuh-Egi?