After you assist with watering the garden in Slitherbough, Runar has more work for you to help with.
This quest is available if you have completed the quest A Helping Hand.
Starting the Quest
Talk to Runar in the Rak'tika Greatwood to begin the quest. There will be a cutscene.
Look Around at the Destination
Go west and through the tunnel to exit Slitherbough. Go south to where the orange arrow is pointing in the minimap. Check on the sparkling Destination to proceed. There will be a cutscene.
Defeat the Sin Eater
Go to the orange circle on the map, then dismount and enter the purple circle. Kill the Forgiven Dissonance.
Speak with Minfilia
Go south to where the orange arrow is pointing in the minimap. Go south of the tree and talk to Minfilia to proceed.
Search for the Jade Heartstone
Go to the west edge of the orange circle on the map and check on the sparkling Pile of Leaves there.
Show the Jade Heartstone to Minfilia
Go to the quest icon on the map and talk to Minfilia to hand over the Jade Heartstone.
Deliver the Jade Heartstone to Runar
You can either teleport to Slitherbough or you can go north until you can go east through the tunnel to Slitherbough. Go to the quest icon on the map and talk to Runar to hand over the Jade Heartstone and complete the quest.
Next Main Scenario Quest
After you complete the quest, talk to Runar to accept the next quest: Saying Good-bye.