Innocentin:
These days the Silver Spear is awarded to whomever distinguishes himself suppressing the insurrection. One is held by the King's royal escort, who recently caught and executed a traitor, and the other spear is held by someone else... someone who dealt mercilessly with the undead insurrection and expelled the filthy devil worshippers!
You'll find him in the temple of Rune Castle Town.
Don't ask me any more. Take your clues and go find out where the key can be used.