This is based on Wikipedia’s plot summaries (which I read under the assumption that any major character deaths would be mentioned), cross-checked with the Redwall wiki. Note that since I haven’t actually read all of these books, and the ones I did read were a long time ago, I’m not sure if all these characters would count as “major”.
I’ve listed at least one “major” character death per book. Some deaths have been deliberately left out (for evil characters, or for minor characters), and it’s likely I’ve missed some deaths.
Not sure it needs saying, but every single death listed here counts as a spoiler in my book.
“Major” death(s), by book, with books in release order
- Redwall: Abbot Mortimer, Brother Methuselah
- Mossflower: Boar the Fighter
- Mattimeo: Lettie Bankvole, Friar Hugo, Queen Warbeak, current Log-a-Log
- Mariel of Redwall: Colonel Clary, Brigadier Thyme, Pakatugg Treefleet
- Salamandastron: Brother Hal, Spriggat, Urthstripe the Strong
- Martin the Warrior: Laterose of Noonvale (Rose), Felldoh
- The Bellmaker: Finnbarr Galedeep, Mother Mellus
- Outcast of Redwall: Skarlath
- Pearls of Lutra: Piknim
- The Long Patrol: Rockjaw Grang, Russa Nodrey
- Marlfox: Nutwing, current Log-a-Log
- The Legend of Luke: Sayna, Luke the Warrior, Ranguvar Foeseeker
- Lord Brocktree: Jukka the Sling, Fleetscut, Lord Stonepaw
- Taggerung: Lady Cregga Rose Eyes
- Triss: Shogg, Drufo
- Loamhedge: Sarobando, Bragoon
- Rakkety Tam: Corporal Butty Wopscutt
- High Rhulain: Major Cuthbert Blanedale Frunk
- Eulalia!: Asio Bardwing
- Doomwyte: Friar Skurpul
- The Sable Quean: Flandor, Brother Tollum
- The Rogue Crew: Swiffo
I remember thinking that this seemed like a deliberate choice on the part of the author, perhaps to add pathos to his stories
Yep, seems like that's intended. This is made pretty explicit in Pearls of Lutra. (For context, this is an ending scene; the heroes have defeated their enemies, solved their riddles, and the adventurers have arrived home)
These pearls are said to be rare, precious and beautiful, yet when I look at them now I see only bloodshed, greed and death. There are many creatures lying dead because of them, from the family of Grath down to countless searats and corsairs. But one touched our own lives deeply, a young Abbeymaid who was friend to us all. Piknim was slain because of these six pearls.
Even in this scene of peace, right before the wild celebrations, Jacques takes the time to remind his readers of the price his characters paid for their victory. This excerpt is quite directly evoking pathos to give more weight to the story by emphasizing its consequences.