C – core set
M – Shadows of Mirkwood cycle
M1 – Hunt for Gollum
M2 – Conflict at the Carrock
M3 – Journey to Rhosgobel
M4 – Hills of Emyn Muil
M5 – Dead Marshes
M6 – Return to Mirkwood
K – Khazad-dûm deluxe
D – Dwarrodelf cycle
D1 – Redhorn Gate
D2 – Road to Rivendell
D3 – Watcher in the Water
D4 – Long Dark
D5 – Foundations of Stone
D6 – Shadow and Flame
H – The Hobbit saga
H1 – Over Hill and Under Hill
H2 – On the Doorstep
N – Heirs of Númenor deluxe
S – Against the Shadow cycle
S1 – Steward’s Fear
S2 – Drúadan Forest
S3 – Encounter at Amon Dîn
S4 – Assault on Osgiliath
S5 – Blood of Gondor
S6 – Morgul Vale
Bard the Bowman (H2), Bard Son of Bain (M4) and Elladan (D2) are all a bit special as they come with the printed willpower of 2 in the traditionally willpower-drained Tactics sphere.
Bofur (H1) and Eagles of the Misty Mountains (M6) are ally counterparts to the above, the former with a side ability, the latter with a powerful Eagle synergy.
There is a wild card in the Tactics pool, Trained for War (S2) allows a strictly Tactics deck (all hero printed resource icons required) to use their attack strength instead of willpower when questing. It is quite some requirement and hardly a permanent solution but it is one way to do for the lack of willpower. The important cooperation note is that all characters (including other decks) will have to do the swap.
Thorin (H1) is the Leadership’s hero leader in willpower.
Dáin Ironfoot (M6) is the basis to the Dwarven willpower swarm strategy, a strategy that gets stronger with every Dwarf that enters play (including heroes and characters of other players).
Faramir (C) is the ultimate willpower booster, no matter what trait or type, he’ll boost them all for any (one) player; but he’s an ally, so not a given, and he’s not exactly cheap, though resources flow better with Leadership.
Celebrían’s Stone (C) was a powerful card in the core set, but its willpower boost has become less stand-out-important since. There’s the Aragorn combo to it, still.
Sword that was Broken (C) has a much stronger Aragorn’s ring to it, so much that it is quite useless without him. It is a strong card whenever much willpower is needed and the said hero is in play but coming in Leadership, Faramir is generally a stronger play.
Rear Guard (M4) is a lesser willpower boosting card. Its use is better in a deck that benefits from characters leaving play (Imrahil, Horn of Gondor, Valiant Sacrifice, Grave Cairn types of decks; most of which are Leadership cards).
Visionary Leadership (S6) is a card that mitigates Gondor's greatest weakness, their lack of willpower. And it turns her cheap allies into much more potent servants.
Éowyn (C) is the ultimate quester… wait, it says battle or siege on the quest card which means Éowyn shall quest for 1? Yeah, outside of battle and siege mechanic, Éowyn is the ultimate quester, if only a bit fragile and not much good for anything else.
Glorfindel (D5) is a renowned character, and he gets mentioned a lot in the game too. Threat cost 5, willpower 3, do you take that hero?
Words like power and creep have been mentioned in one sentence when Arwen Undómiel (D3) arrived in the middle of the second cycle. You get 2 willpower for 2 resources, core set players find that very, very good. With Arwen, however, you get a very, very useful ability as a bonus. Is she fragile? Not overly so for the cost of 2.
Silvan Refugee (S2) is the only ally to date with the printed cost of 1 and willpower strength of 2. Of course, there's a drawback to that but the stats are amazing.
Escort from Edoras (M3) is a one-trick pony, if ever there was one in this game. There are no battles and treacheries hurting questing characters? Then this guy is worth it.
West Road Traveller (M6) is less potent than the above but should stick around more; the ability will occasionally see play too.
Not surprisingly, Spirit contributes to the Outlands deck by increasing willpower, namely Ethir Swordsman (S1) shall give all your Outlands characters +1 willpower strength.
Bofur (D1) means there’s a chance to have a 2-willpower ally for the price of 1; but not always.
Pelargir Shipwright (S4) is quite perfect for mono-Spirit decks, he shall give you 3 willpower for the same cost; his 3 hit points and additional point of both attack and defence strength make him so solid.
The Favour of the Lady (C) has a lovely art but is spelled without “u” on the card, which goes very much against Tolkien’s text. As for the game mechanic, it is hard to see this card ever included if not for the looks or theme; giving +1 willpower for the cost of 2 is just not good enough even though it will almost never hurt you (and there are instances when having a very strong quester as opposed to many weaker ones is beneficial).
Untroubled by Darkness (K) is situational by default and redundant in a way, especially with Dáin around.
Astonishing Speed (M6) might have been meant as a Rohan card to put all that Mirkwood cycle’s worth together but if it is one thing a Rohan deck can do, it is to quest well for willpower – and without this card; what a Rohan deck needs… is many other things.
There are two Elven theme events coming late in Against the Shadow cycle, Children of the Sea (S5) provides some new thoughts about ally recycling, and it seems to combine perfectly with Silvan Refugee (S2), an Elven ally that is a great willpower booster on its own. Secondly, Lay of Nimrodel (S6) doesn't require Elves per say, just presents the theme, and boosts a Spirit hero's willpower (if that is ever needed).
Elrond (D6) and Glorfindel (C) have willpower of 3 and are worth mentioning for the fact.
Erebor Record-keeper (K) and Henamarth Riversong (C) cost 1 to play and their willpower is also 1, which together is a rare feature for any ally.
Gildor Inglorion (M4) can give you a good advice, though not always gladly; he can also tell you that there is a Lore ally whose willpower is 3.
Lore is great for drawing more cards than what is ordinary. But it is not great at producing extra resources. It can thus happen that you end up with more cards than you’ll be able to play, why not discarding a few via Protector of Lórien (C) to boost your willpower?
Gandalf (C) and Gandalf (H1) are two (or are they?) examples of allies with a very high willpower.