Right, so, there was a request for me to make a list of all the important people who have died over the course of Songs of the Spheres. Here they are, sorted by arc.
Not including anything in arc 10 or beyond.
ARC 1: BREATH
No major deaths. It was all sunshine and rainbows for a while there.

ARC 2: HEART
Some of the Elements of Insanity (Derpigun, Pinkis, Applepills), and the Rarispies.
The Pinkie Sage and the gods she fused in her mask
General Sunset
Majora

ARC 3: LIFE
Twilight Sparkle of Equis Vitis. She was replaced.

ARC 4: HOPE
Sweetie Brute
Sparky
Fef
Celestia
Siron
Ganondorf
Joseph Joestar
Aang
Zuko
Queen Luna
Dio (again)
The Equis Vitis Leaders that aren't Thorax or Princess Luna
And a lot of other leaders.

ARC 5: LIGHT
Granny Smith
Enrico Pucci (...he SORTA mattered)

ARC 6: MIND
The Collector
Davepetasprite
Lieshy
Lileur

ARC 7: BLOOD
Iroh (depending on how you look at it)
A bunch of people who came back somehow because Homestuck.

ARC 8: RAGE
Skarn
Brell
Arthon
Rainbow Dash
Thor
Olivia/Sombra
Havocwing
A lot of minor characters. It was war, after all.

-GM, master of culling.

What about General Sunset?

6540195
Holy cow it's been so long since I wrote her that I forgot she existed. Derp.

-GM, master of derpidoo.

I have a sneaking suspicion that this may need updating.

I think this needs an update again

7080712
It does, but honestly, at this point it's just ridiculous so I'm not inclined to update it. Out of laziness more than anything.

7080715
Fair enough

wh4t now?