In the Battle Tortoise pens, northwest of the Grand Tree When you have killed all of the Evil creatures, go speak to the King, and you will finish the quest. You can turn your Crystal seed into aCrystal Sawby going back to the Singing bowl in the cave and then choosing the Sing-glas...
this might prove challenging. Some advantages of this relic falls off towards the late-game as everyone gets access to the no-cooldown memory crystal which can teleport you back to the last location you saved. So they
Now, enter the western room and use the key on the door, then again on the next door. Plant the Consecration seed close to the grave and a small crystal tree will appear. Return to Islwyn and Eluned to claim your reward. Congratulations! Quest Complete!