Mustering the Rohirrim can be a very powerful card in the right deck. It's pretty much the best way to search for rohan allies (especially Eomund/Gamling), besides just straight drawing them, and should trigger every time (if it doesn't you probably don't have enough targets). It is a bummer that it adds only one to hand instead of all targets found, but is still a good search effect.

Well this ain't a bad card and one of the must have for Rohan deck for sure, but what immediately pops up in my head is comparison to The Eagles Are Coming! from Eagle deck. On one hand it cost something and gives you only one card, on the other hand it goes quite deep into the deck in searching. At the end what makes this card good is the synergy with other sphere cards like Gléowine, or Snowbourn Scout which are still best Rohan trait cards for me so far. The artwork is great. Verdict: 4/5.