Go to the priest in underwater Ys and ask priest help, then ask priest morgen. (The Ruins of the Foodstores)
He will blabber on about how morgens are the worst and then ask you if you want to help him. Ask priest yes.
Hunt warden and kill him to get the key from his corpse.
Hunt grouper and use the key from the warden to unlock the prison. You will need pick lock to open the cell that the grouper is in.
Kill the grouper and he will spit out a corpse. Get book corpse.
Note: there are two corpses here now. If you want something dropped by the grouper, check 2.corpse.
Go back to the priest and give book priest. He will tell you to put it back where it belongs.
Go S 2W S E from the priest and put book library. The shade of Plato will appear.
Ask plato defeat and he will tell you to get a horn from a cave in the north east.
Go to the cave (E 2N 4E N 2E N from Plato's library) and get the horn that is lying on the ground.
Note: it will not appear if someone has recently picked it up.
Go to the balcony over the great dike (S 2W 2S 3W 3S E S 3W S 4E S W U S from the cave).
Note: The next step will spawn some difficult mobs. If you want a chance to get ready, then move north immediately afterwards.
Put horn pedestal.
This will spawn two morgen raiders. After killing them, two more will spawn.
After killing the second set of raiders, the horse, Morvar'ch will spawn.
After killing the horse, Queen Malgven will spawn.
Note: you must land killing blow.
Upon dealing the killing blow to Malgven, your name will be announced on info and the priest will whisper to you to come get your reward.
Go to the priest and ask priest reward.
You will receive Xp, a whois, a random scroll, a random seal, and your name will be announced on info!