Alright, loredump time.
As you might have guessed, all the lords have different powers and theme (For the sake of simplicity I'll be referring to them by their masks, because their actual personas are malleable).
- The mask of law is paladin-like, using smiting and self-powering buffs to make their melee attacks more powerful.
- The mask of chaos is more like a wizard, enabling them to cast powerful spells, mostly based around debuffing opponents, but is also capable in direct combat.
- The mask of war has very little in the way of actual magic, and instead is simply extraordinarily strong in many forms of combat and tactics, but has very little skill in the way of long-term strategy.
- The mask of the owl (The one with an eye) is a strategist; weak in combat, but knowledgeable, quick, stealthy, and capable of incredible feats of divination.
- The mask of fire is...Guess. Skilled with directly damaging magic. Despite the reputation of fire, it's actually rather clever, preferring to act suddenly and quickly.
- The mask of ice is specialized heavily with a spear and shield, preferring to soften enemies with minions before enacting the coup de grace. Uses little magic, but when it does, generally obscures sight and uses AoE clouds.
- The rosen mask is compassionate and capable of healing even fatal wounds. This mask was not seen during the game; I'll get to it shortly.
- The king's mask is again a noncombatative one, instead being seductive and silver-tongued. It was the original mask; all further ones are vestiges of it.
So, what's with the king and rosen mask? Well, you'd only actually met six of the seven lords: the one with the blank mask was in fact the king. The seventh, the rose, was dead, and their mask held deep in the caverns, protected by various deadly traps, monsters, and illusions. It was slain by the other lords because the rose didn't want to bring about the apocalypse, as the others did; instead, it turned against the other lords, and was destroyed as it was a threat to their plan.
The king mask was the first to be made, carved of solid silver by a skilled artificer. Initially, the plan was to allow it a mind of its own to aid the wearer in matters of royalty, commissioned by a powerful baron. However, this failed; it grew too powerful, and too evil, and betrayed its liege. The mask, still controlling the now mindless body of the baron, sought to destroy the world and all therein, to remake it with itself as a god. Presumably, with the campaign ending as abruptly as it is, this was successful and happened a little ahead of schedule.
The king mask effectively split itself into seven more pieces (Not physically of course; it's still whole, just with pieces of it's 'soul' spread about). These were presented to powerful figures throughout Nazerian history by the mask, wearing the long, flowing, concealing robe that the lords came to be known by. They too turned against their bearers, and soon the king's army was formed, each powerful and skilled in their areas. Of course, though the mask greatly extends longevity, they aren't immortal; various wearers have died and new individuals have worn the mask, hence why I refer to them by the mask, rather than name.
The campaign likely will have ended in one of three ways: The players would free the demon sought after by the Rebels and with its aid, destroy the lords. The demon would still rule over the world, but at least the world would still be around. Alternatively, the players would mange to slay both the lords and the demon. This would be by far the most difficult ending to achieve, but also the 'golden' ending. Finally, the players may have found the rosen mask, worn it, and used the power of it to fight back against the lords. However, over time, the rosen mask would continue to grow crueler, and eventually would reform into a semblance of the king mask, merely delaying things. Naturally, the campaign could have gone other ways, but these were merely the routes I'd meaningfully planned for.
Also, though it never came up in this thread, I was intending for one of Immaterial's vestiges to actually be the ex-rosen mask, guiding the party towards the place where it's held.
If you have any other questions, feel free to ask.