William West, Elliot Nightray, Vanessa Nightray, Hans, Ernest Nightray, Fred Nightray, Claude Nightray, Bernard Nightray, Isla Yura, Xerxes Break, Vincent Nightray, the Intention of the Abyss, Cheshire, Xai Vessalius, Sheryl Rainsworth, Fang Baskerville, Echo Baskerville/Noise Baskerville, Oscar Vessalius, and Rufus Barma.
Deaths that are implied during the epilogue of volume twenty-four include Sharon Rainsworth, Reim Lunettes, and Ada Vessalius.
Deaths that occurred before the time of the series but that are mentioned/shown are Raymond Nightray, Jack Vessalius, Oswald Baskerville, Lacie Baskerville, Rachel Cecile, Sara Vessalius, and Levi Baskerville.
Oz and Alice technically died but were resurrected.
There are plenty of nameless side characters who died as well (ex. children from Fianna's House who were Contracted with Humpty Dumpty) and irrelevant deaths that obviously happened because of how the mentioned characters were alive so long ago (ex. Calum Lunettes) that would be difficult to remember and mention, not to mention pointless. Have I forgotten anyone?