Goblin Slayer: Side Story Year One summary: A prequel series that reveals Goblin Slayer's past and the events that led him to become an adventurer with the sole purpose of exterminating all goblins from the world.
Goblin Slayer Gaiden 2: Tsubanari no Daikatana manga summary: Goblin Slayer Gaiden 2: Tsubanari no Daikatana is a spin-off series of the main Goblin Slayer! light novel. This is the manga adaptation of the light novel. Set 10 years prior to the original series, the story centers around Sword Maiden's party of six adventurers on their journey to the Dungeon of the Dead to kill the Demon Lord.
From Yen Press: A young priestess has formed her first adventuring party, but almost immediately they find themselves in distress. It's the Goblin Slayer who comes to their rescue--a man who's dedicated his life to the extermination of all goblins, by any means necessary. And when rumors of his feats begin to circulate, there's no telling who might come calling next... Adaptation of the Novel "Goblin Slayer"
Goblin Slayer: Brand New Day summary: Goblin Slayer has enjoyed many an adventure, but the people around him have adventures of their own!
A new spin-off from the wildly popular Goblin Slayer series following the lives of the many other characters Goblin Slayer and the main cast have encountered throughout their adventures.