Refresher on how classes use Aether?

[Ramesses]

Thaumaturgy uses the body's own aether to cast spells - as can be seen in the class questline with the sibling of the guildmasters who want to learn thaumaturgy, but has too low aether.

...The DoM classes probably do so as well.

Well said, and yes, the DoM classes indeed do so. For instance, Blackmages (developed in the Fifth Astral Era) use their own bodily reserves of mana to fuel their powerful incantations but can also use their aetherial bodies as "conduits" to tap into Hydaelyn's reserves of life energy to launch their arcane spells.

Likewise, Summoners (developed by the Allagans in the Third Astral era) basically transform the essences taken from defeated primals into aetheric allies... what we call "egi".