A strange young man, both brave and unstable
- What's that, you say? Impress you with feats of manly violence?
Slak approaches life in the Pit with a carefree and reckless attitude and a questionable amount of sanity. His lack of apparent intelligence at one stage lead Azra to note once how he lost an argument with a rock. He is also very egotistic, intrusive, and vain as indicated by his entries into Azra's journal. He also considers himself a bit of a ladies' man. Slak also has little idea of dedication to mundane work and at one point is left on Guard duty only for Markos to find him failing to take the role seriously during Return to the Shadows.
Slak is a big fan of "manly violence", and openly dislikes the idea of using armor, going so far as to remove his pants to make a point before Deeper Into The Stronghold. He also has hygiene issues and extremely bad body odor, and several of the characters mention this including Azra and Markos. This is also extended a little to food; at one point Niru tells him the sheep stew he had eaten was regurgitated by her for her children; he pauses for a moment then asks for more. He dislikes eating vegetables, and even briefly suspects the Selini monks of attempting to poison him when served with "those things that grow out of the ground".
Little is spoken about Slak's background.
Azra's Day 4 entry talks about Slak's background after Azra finds a letter on a particularly rich parchment. Azra is unable to finish reading it before Slak consumes it screaming about how it was all "Lies!".
It seems Slak was suppose to attend university in the land of the Carcassians both for his benefits and safety by order of his rich father. However, much to the anger of his father it was soon discovered by his father's agent that Slak had left and paid a Nomad to attend university in his place. This is likely the reason behind Slak's abilities to read and write, though what caused him to abandon his life of privileges is unknown.
When Arza meets him, he is surviving much on his own on whatever life brings him, having survived the Plague at some point without being turned into a revenant. He was needing a fresh pair of boots and was in the process of stealing hers when he was called into battle.
Slak's main reason for tagging along with Azra revolves mostly around the fact he gets to kill things. He does not always take her seriously. He also constantly writes "random" stuff in Azra's Journal which appear from Day 3 onwards in Game+. This comes much to her surprise as she can't comprehend how someone like he came to have an education. His randomness and intrusion constantly leads her to hitting him on the head with a ladle.
Ketta and Slak have a particular relationship. Ketta claims that Slak owes her quite a bit of "junk" (the currency of the Pit). Slak also mocks her, even when he adds a entry into Azra's journal written on behalf of Ketta, leaving her to wonder why her name was taking so long to write. When Ketta is given the option to leave the Pit (when the choice is given for Ending A) she tries to convince Slak to come with her, to which he declines. Slak sees both her and himself as survivors their entire lives, but unlike Ketta accepts this will not last forever.
Once Markos enters the group, Slak mocks him for wearing armour and constantly puts him down, even long after he joins the group he still refers to him as "the new guy". He also mocks the relationship between Markos and Azra, and at one point adds writing to a letter claiming that she (Azra) wants Markos' children. Markos ignores his entries though this incident earns him the fury of Azra's ladle.
- According to New Game+ secrets, Slak was originally designed as the librarian character. His role was switched out for Azra. In his profile it was said he hated applied maths and science but was well educated loving the subjects of history and epic literature.
- Slak originally carried his sword on his back not around his waist, this was the same for all the berserk-class. However, this was changed after it was pointed out that this would make it difficult for he and his fellow beserkers to draw their swords in battle. Though the in game art and sprites were changed, Slak can still be seen in the game intro screen with his sword on his back.