So here's the list of them from post #1, with who claimed what, and whether they're still active or not.  Also, posting by character name, not username.

Cosmog/Cosmem - Chuck/Mike
Solgaleo - Jenn
Lunala - Jenn/Shiranui/Mike
Nihilego
Buzzwole - Shiranui/Veronica
Phermosa - Sashia/Veronica
Xurkitree (there are 2 of it) - Sashia
Kartana (4 of it) - Chuck/Shiranui
Celesteela (there are 2 of it) - Chuck/Jay(left)/Sashia
Guzzlord - Shiranui/Noel
Necrozma - Jenn/Mike/Noel
Tapu Koko
Tapu Lele - Veronica/Noel
Tapu Bulu - Chuck
Tapu Fini - Jay(left)/Veronica
Magearna
Marshadow - Chuck/Sashia/Noel
Poipole/Naganadel - Chuck/Mike
Stakataka - Shiranui/Veronica
Blacephalon
Zeraora - Chuck/Noel
Type: Null/Silvally #3 - Chuck (1 is owned by Gladion, 2 is owned by Mike)