Éogar, son of Hadorgar is the Horse-master of Hengstacer Farm, in Bree-land.
He sells starter steeds for 200 and various other steeds requiring the Riding skill, which can be acquired by a quest from him from level 20.
Discovering the Descendant quests:
Buying a steed for 500 silver from Éogar also gives the character the Mount Discount skill that grants a 60% discount on future purchases from him and some (all?) festival mount traders.
* Men of Bree Vendor Discount (5%) + previous 60% = 65%
- "Welcome to Hengstacer. Here I breed the finest steeds in all of Eriador."