The Blackgards have infantry, cavalry, as well as naval units. Press question mark to learn the rest of the keyboard shortcuts !It's actually more interesting that Rhaegar and Lyanna are actually in all likelihood related given that Betha Blackwood (Rhaegar's great grandmother) was probably Melantha Blackwood's (Lyanna's great grandmother) sister. His role as Robb's chief northern advisor is taken up by Lord Roose Bolton. They are one of the premier houses of the Riverlands, and former royalty it seems.What exactly do you want to know when you say, what is the deal?Is there any house that didn't use to be kings? And that if Melantha and Betha were sisters, then Rhaegar and Lyanna have the same great great grand parents in Lord Blackwood and his wife.I think Jamie and Brienne will end up there in the next book somehow. The land troops of House Blackgard are divided into The naval counterpart of the Blackgard armies were collectively commanded by three admirals, until The cavalry of House Blackgard are renowned and battle-hardy. House Blackgard of Ebonheart is a Great House of Westeros. It seems tied with Bloodraven somehow though we don't know why or how just yet.So all that said, House Blackwood seems like it'll come into play in the future though I doubt it'll be anything of great importance as far as things like Tytos Blackwood or his family becoming huge characters.
It makes me wonder if the Wolfswood was originally named the Blackwood, before they were driven out. Ebonheart is their seat, it resides in the eponymous port city of Blackgard, far to the east of Westeros. House Blackwood is historically linked to sorcery, exemplified by Bloodraven. The Reeds and their vassals are Crannogmen, a distinct offshoot of the First Men who have adapted to living in the swamps of the Neck. Their lands are the Borderlands, a long stretch of land that originally belonged to the Stormlands. Thanks for the reminder!They do seem to have some larger importance that is yet to be revealed.The Blackwoods are originally from the North and still keep the Old Gods even though they're a "southron" house at this point. Maybe they'll run into the Blackfish.The house is originally from the Wolfswood in the North, they have mostly First Men blood, which explains why they follow the Old Gods and why they married Starks. In the Warg King, it's stated the Starks killed all of them, but that seems unlikely.
(Not that the Blackfish couldn't have been there anyway. They guard the borders that separate the Stormlands from the Reach and the Crownlands and oversee all travellers looking to leave, or enter the Stormlands. House Reed is the southern-most house of the North. The horse-riders fall under the command of a legion, but are usually better equipped than their infantry counterparts.