it befriended you but it was about to be attacked by the bounty hunter named Stalker that was hunting it down, after seeing it's friend get hurt it decided to fused with you to fight Stalker after the fight they defused back into themselves, in this form it has the same abilities as it's base form. And in order to transform into that form Slimeball has to fuse with someone and it has the choice to defuse back into it's base form