Endless Bounty Karth Happy Ending Guide

Step 1: Save Gerald first until he leave for ThorendellTechnically you need to sell only 5 items.
Collect All the Mushroom
Collect the ring from the dead husband skeleton in the Mines
Collect Moist Moss from the Gerret Falls
Extra : click on the crate at the beginning segment two times to get GOLD ORE
Talk to fishing guy to activate Stone Snail quest and collect stone snail
Extra note: you can unlock the greedy Achievement if you sell of the quest items to Karth.

Step 2: Sell all the items to Karth
Step 3: Buy Information and then ask about Karth himself
Step 4: After selling 5 items and asking info about him. He will ask for Oil demo, say yes.
Step 5: After Oil demonstration Buy the Oil for 75 Gold.

Extra: Spend 30 gold in the Inn to use the Oil

Step 6: Don’t forget to ask the Inn Keeper Lozran about Karth, he will say something like “I don’t trust him, he’s shady blab la bla.” This will unlock new convo with Karth. “Just want to talk”

Step 7: Keep talking to Karth multiple times on all topic eventually new topics will pop up about orphanage, and the future.