Mount of Dernhelm/Eowyn and Merry/Master Bag, that
went all the way through the charge on the Pelennor fields until
encountering the Witch-king.
Quote sent in by Dior-(V)
the great grey steed
Windfola made little of the burden; for Dernhelm was less in weight
--"The Muster of Rohan", Return of the King.