This is a WIP deck, in the sense that it's intended to be used for some kind of "progression play" through the Ringmaker cycle - the only cards from this cycle in this version are the ones from the Voice of Isengard box and Celebrimbor's Secret.
It is a fairly straightforward deck intended mostly for solo, that focuses on the use of mounts and Rohan allies going in and out of the battlefield (hence the "light cavalry" theme).
Éowyn is the main quester and the primary target for (of course) Windfola, Celebrían's Stone and generally speaking any attachment that increases her willpower - she can solidly quest for about 7 or 8 alone when set up. Her discard ability come in handy later in a game, when additionnal unique attachments start appearing. Golden Shield is mostly situational because it competes with other restricted attachments and, in normal situations, is a good discard target. Eowyn also provides for repeatable discard actions from Rohan allies through Stand and Fight. Finally, Westfold Horse-breeder is here to get the mount machine running.
Éomer handles attack and synergizes with the discard actions of other Rohan allies. The Westfold Outrider in particular is meant to synergize with his ability and Quick Strike or Battle-fury to engage and destroy enemies outside of the normal combat window (the latter being especially useful when Rohan Warhorse isn't in play). Charge of the Rohirrim can further increase his attack power.
Elfhelm provides first and foremost the passive effect that renders mounts like Windfola much more useful than they technically are. He is also sort of the main defender, not really because of stats but because he is the only target for Armored Destrier, which essentially enables him to defend twice in a round. He pays for Snowbourn Scout which is the obvious chump blocker here, as well as for situational card draw with Valiant Sacrifice and situational resource generation with Captain's Wisdom (which can synergize with Heir of Mardil).