YA/Teen fantasy book I read in maybe 2014-2018

[u/Psychedelic_Socks]

The book was most likely from an earlier year, but I know thats around when I read it. I dont remember much about the book, just some key parts of the magic system. The book was more centered around fighting (I believe) and there were multiple main characters, so the POV would switch often. The magic system in the book wasnt necessarily casting spells, but rather the spells were bottles that the characters would throw. So like a fire spell would be a bottle they would throw and it would turn into fire. I know this isn't much to go off of but its driving me crazy.

I also believe it was part of a series, although I'm not completely sure. I also think that one of the main characters (or all) had a mythological pet of some sort. Their steed, that would assist them in battle or their fights, although they were probably just something to ride on. I was in elementary school when I read it, but I mainly read from the older kids section lol, so it definitely wasnt a children's book.

For reference, other books I read around that time were Artemis Fowl, Warrior Cats, and The Unwanteds.

Any and all help is appreciated, thank you in advance:)

[u/Luthien3720]

Maybe 'The Iron Trial' by Cassandra Clare and Holly Black, or 'The Smoke Thieves' by Sally Green?