Overview:
This is meant to be a fun, fairly thematic deck intended for solo play, but should work fine for multiplayer as well. Radagast is of course well-known for his love of animals, but he's also good friends with the Beornings, so it only makes sense that he should work together with both. Mablung is admittedly included primarily for resource generation, but it does make sense that a ranger might be found working together with these folks. I've included as many questing allies as possible, as that's obviously what solo struggles with. I wanted to include more Beorning allies to be more thematic, but unfortunately Beorning Guardian & Beorning Beekeeper are simply not useful enough to be included in a solo deck - they could potentially be included in multiplayer, however.
Gameplay:
The main goal here is really to get out a Giant Bear or two (or Beorn), which can really turn the tide. I've found that it's best to pay full cost (or hopefully get a discount by finding Radagast's Staff) for Giant Bears & even for Beorn, even if you already have a Beorning Skin-changer in play. The reason is that the skin-changer can quest, and even though it's only for 1, every single point is helpful in a Tactics-heavy deck. Use the Giant Bear to defend, and if it dies, then use a skin-changer to bring it back from the discard pile. I find this is the most efficient & effective use of the Giant Bear, and although it might sound expensive, this deck doesn't have too much trouble generating resources thanks to Mablung.
Meneldor is also very helpful with questing, and you can pull him back with the Flight of the Eagles, so that you can make maximum use of his special ability by re-playing him from your hand. I know that most deck-builders put Word of Command, Wizard Pipe, and Daeron's Runes with Radagast in order to make the deck slightly more efficient, but I've designed this deck so that it can function quite well even if Radagast doesn't have his staff, as the Tactics heros can pay for most of the creatures, and most of the Lore cards are low cost. As long as you can get a creature out every round, Radagast quests for free, so sometimes it's good to hold back a bit and only play one even when you could play more. If you don't have any creatures in hand that you'll be able to afford, but a Messenger Raven is in play, make sure to recall it. If you don't have the staff yet, pick 'Attachment' with the Raven's ability - it's not a big deal to lose an eagle, a Giant Bear, or Beorn, because Gwaihir and Beorning Skin-changer can bring at least one of each back. I typically only pull the Raven back if I need to, and I use them primarily as cheap questers rather than for their special ability.
Gandalf is included purely for threat reduction, which is another major issue with this deck. If you're playing multiplayer with a deck that can take care of threat reduction then it's probably best to replace Gandalf with attachments or events.
Other Options:
I've listed Éowyn and Legolas as possible alternate heroes to replace Mablung for quests that might require more questing power. I haven't tried either of them with this deck, however, and losing Mablung's resource generation might be a problem, especially early in the game. Allies like The Riddermark's Finest, Henamarth Riversong, and Wild Stallion might also be useful to gain a bit more questing power.