Ally Rolls in The One Ring

It's funny what kinds of rules gems you can find buried in unexpected sources.  In the second adventure of Tales from Wilderland (Of Leaves and Stewed Hobbit) there is a scene where the PCs are supposed to make a stand in a defensible position (the ringfort) with a handful of allies.  Enemies swarm the ringfort, and the battle description contains a table that describes how the allies fare in battle.  This "Allies In Battle" table (pg. 34) keeps things moving quickly, preserving a narrative focus and making it unnecessary for either the Loremaster or the PCs to take control of extra characters.

In the play-by-post (PbP) game that I'm currently running the PCs ambushed a large orc camp backed up by 2 units of Elven cavalry, a handful of Barding archers led by the Barding PC, and a handful of Bardings disguised as orcs led by an exiled Dwarf PC who escaped a brutal captivity in the hands of orcs.  Obviously that's a LOT of individuals to keep track of, and the need to abstract the mechanics for the battle were even greater considering that Legolas himself led one of the Elven units, and I didn't want to open up a can of worms by statting him out.  Remembering that table from the short campaign that I ran for my regular gaming group (relevant posts under the TOR-C2 tag), I decided to adopt it for this battle.  

While the table from Tales from Wilderland offers specific results for the battle that it applies to, it was immediately apparent that the results could be tweaked on the fly to apply to virtually any combat, with any number of allies and enemies.  Here are the basics, in a nutshell:

The Loremaster rolls a Feat Die (the special d12; for those using regular dice, the 11 counts as an Eye of Sauron and the 12 is a Gandalf rune).  

• If the Eye is rolled something really bad happens.  For a smaller number of allies this will usually mean that one of them is slain.  For larger "units" this could mean that multiple individuals are slain, the leader is slain, etc.  Whatever is dramatically appropriate.
• On a roll of 1, 2, 3, or 4 the enemies are doing better than the allies.  This might be represented by one of the allies suffering a wound (or being slain for larger groups), one or more enemies slipping past them to attack a priority target (probably one of the PCs, even one in Rearward stance), or a change in the tactical landscape.  For example, if there are any modifiers in place due to the Complications table (pg. 48 of the LMB, or the GM screen), these can change to favor the enemy.  Additionally, a 1 should probably have worse effects than a 4 (in TfW bad stuff triggered if you rolled under the number of allies, but obviously this wouldn't work for larger groups).  
• On a roll of 5, 6, or 7 the allies hold their own, but don't necessarily gain any ground.  Nothing particularly interesting happens in this round, or if you'd prefer to narrate changes in the battle they should be net zero.
• A roll of 8, 9, or 10 mirrors 1-4 in that now the allies are doing better.  Depending on how many enemies are present and/or how fast the LM wants the pacing of the battle to be, this could mean that an enemy is Wounded, an enemy is slain, or the allies gain some sort of tactical advantage (there should always be a good narrative description for this, but it can be mechanically represented with that Complications table).
• If a Gandalf rune is rolled, the allies are doing extremely well.  Perhaps an unwounded enemy is instantly slain, multiple enemies are slain or flee, an important enemy (perhaps a leader) is slain, or in some circumstances the LM might allow one or more PCs to regain a point of Hope as the tides are turned (though this should be used very sparingly, and you should have a good reason for doing so!).  

Some Notes

These numbers are consistent with those from the table in TfW, with the results more generalized.  But these can easily be changed based on the details of the battle.  Are the allies severely outnumbered or in a rough spot?  Maybe the numeric results are broken down like this:  1-6 is bad, 7-8 is neutral, 9-10 is good.  In fact, it's worth pointing out that the originally published values are skewed toward the enemies (1-4 being bad vs. 8-10 being good), and I think this is important.  Since the allies are statistically in a position to lose the fight, it drives home the fact that it's ultimately up to the PCs.  They're the heroes, the stars of the show.  

Along those lines, it's a good idea to offer the possibility of adding modifiers to the roll.  These can absolutely be player-driven.  A successful Battle roll might allow a PC to direct his allies to higher ground, providing a +1 bonus to the Ally Roll.  A Great Success on an Inspire roll might give the allies a second wind, with a +2 modifier to the roll.  A Healing roll might allow a PC to bring wounded ally back into the fight.  Conversely, you can add a penalty to the roll to represent a new advantage gained by the enemy.  If a PC is knocked out and their opponent(s) join the fight agains the allies, that might be a -1 penalty.  The same logic obviously applies to reinforcements.  And if you're stuck on how to adjudicate an Eye result by a player taking a risky action, why not make the allies pay for it?

Finally, you can give the battle some tactical "texture" by having multiple groups of allies (as is the case in my PbP game), with each group getting its own Ally Roll.  This can give PCs an interesting choice to make as they need to decide which ally group to aid, if any, and it allows the victors from one group to affect another group, or the PCs and their foes.  It's perfectly reasonable for a good result on an Ally Roll to result in a combatant breaking off from that "unit" and joining the PCs with its own individual stat block (this is especially useful if one of the PCs is knocked out, as it can give that player an ally to control).