Youll find gekh coal in the decrepit village and getting on his good side isnt too hard, just need some smooth talking. A good persuasion check works or if youre a drow thats even better since he likes his own kind. The interesting part is that helping him means retrieving some fancy boots from thulla, who took them and ran off to ebonlake grotto.

Getting to grymforge is the main goal here and gekh's got the transport you need, so playing nice has its perks. Thing is, helping a slave trader might not sit well with some of your companions, especially wyll or karlach who'll definitely have something to say about it. If youre feeling more righteous, taking him down works too since you can still use his raft either way but helping the myconids might be more your style then.

Neat thing to know, those boots of speed are worth grabbing regardless of what you do with gekh, and theres always a way to get them whether you cure thulla's poison or get creative with your fingers. Just remember whatever you choose here is gonna echo through your relationships with various factions, so pick your path carefully.