Gierrod is a Jotunn.
Gierrod came home drunk to find Magnus Chase, Samirah al-Abbas, Hearthstone and Blitzen. They ask him if he has Thor's weapon, which they assume is Mjølnir. He agrees if they play catch with hot coal, he will give them Thor's Staff. Magnus states they killed his daughters, which angers him and causes him to throw support beams at them until the ceiling collapses, crushing him to death.