Whenever I talk to Grendel to finish this quest, I get the little effect around you that shows that you finished a quest, but I didn't actually finish it. I keep trying to talk to him to try and finish it, but the effect just appears and nothing actually happens. I kind of need this because it gives you 60 pots (30 MP and 30 HP), and since I just started this game, I don't exactly have the most money.
The quest is bugged, leaving a party if you're in on/relogging might fix it. If it doesn't, the quest is most probably bugged. Report the bugged quest if it isn't already!