Near the start of the game you find knifebois lab and you meet him
At this point you can choose to attack him (which starts a battle) but he'll fight you anyway if you killed Larry previously
If you kill him you get the teamaker (his mech suit's blaster) and the abyssal amour
If you choose not to fight him he asks you to get rid of the amalgameme that's taken over his lab's basement (he gives you the abyssal armour so you can breathe in the meme-infested lab basement without inhaling toxic gas) and you can fight the amalgameme after going through the lab basement
If you kill the amalgameme, knifeboi lets you keep the abyssal armour (you can use it in other locations) and gives you the jetknives (throwing knives with jet engines)