Paragon tier should put the players in the driver's seat. They should be lords and masters themselves, and be seeking their own land, title, and poilitical power- OR, whatever other agenda they have.
To really make it paragon tier, you should make sure each PC has a big, major agenda. Talk to them about what they want their pcs to achieve, and emphasise that 'beat the bad guys' is not what you're after.
From this, you should have a set of plotlines you can rely on as well as your own plots. On top of whatever the villain wants, you have what the PCs want. They might go to a city to stop the villain's plot, but they might also go because, for instance, one of the pcs is a priest that is trying to cause a reformation of the church of the silver flame.
It's really down to the pcs and what they're after. Even if players are hestiant to have these kidns of agendas, getting them into this kind of play is what paragon tier is about.
So what kind of PCs are we talking about here?
Do you all mind if I just throw out some story threads/ideas? Maybe you can help me make them suitably paragon and wrap up in a suitable epic tier showdown.
More info is always good on threads like this, if you're happy to get feedback.
Here's where the story is ultimately headed:
The paragon tier bad buy is a rakshasa, Shakul, a claw of khyber who serves the Shadow in the Flame, and is trying to free him.
I'll talk about his plan below.
The party has been gathering artifacts of a legendary hero, the nemesis of the main bad guy, because he is needed to defeat Shakul. They need the artifacts before they can attempt to resurrect him, and the plane of the dead is remote.
No offence but I think this is a really poor idea.
It's a classic example of a plot that might work in a story but does not work well in a game. It's also a classic example of the kind of plotline many people don't see a problem with because the damage done is often intangible.
The fate of the world should rely on the pcs, not some NPC you made up. They're the heroes and should be the focus of the story, not him. An artifact hunt might have been a good plotline, but contrary to what some people will tell you, it's not a good idea to make the plot about npcs. You need the players to be more proactive, not less, if you really want paragon tier to be paragon tier.
It's also very difficult to tell when an idea like this is going wrong. Players might seem fine with the idea- they can use all the help they can get, and it's only logical to use such an asset- but it makes the game less about them, and relegates them to a secondary position. I'd challenge you to really re-think this entire plot, put aside your attachment to it, and consider what you really want the game to be about.
It should be about the PCs. They're the heroes. They're who the game is about. Not only should it be about them, but it should be about them doing thigns their way.
I would argue that even if they resurect this guy, he should be sidelined almost completly. If anything i'd say that he should be made into a deliberate support character- like a smith destined to craft the weapons they use. If he's an ancient hero, then his role is to train them, and the way he died means he cannot take a direct role in the battle (and may indeed simply be some kind of spirit of visitation).
I cannot stress strongly enough how bas an idea it is to make the PCs second banana to some ancient hero dude. You might be aiming for king arthur but you're going to end up with elminster.
Shakul has been sowing the seeds of a breakout of a new war. Once the five nations are fighting, he has an invasion army preparing to march through the Eldeen Reaches to seize Flamekeep.
A good rule of thumb here would be one quest per nation. In each nation, he has a unique servant who has a unique plot to drive the nation to war. Finding and defusing each plot should give variety and have a bit of a 'grand tour' angle.
Add to this, the formation of his army. Certainly, give him a strong core to march out with 'on the day'- but he should also be seeking allies, and the PCs should work to prevent this. This could be as simple as taking out his allies, or as complex as trying to turn them to the heroe's side, despite their wierd and inhuman viewpoints and such.
Hmmm... the mournlands idea...
I have an alternative suggestion for the mournlands and the plane they need to bring into alignment, and the hero guy.
As noted above, I think the hero guy is a mistake to bring into the game. I think a better bet would be for him to be serving in a support and advistory role. So how about this as an alternative, using the mournland.
The mourning was caused by the vaillain, who created a dead spell of death to destroy his nemesis, the hero.
They created a condiuit to the plane of the dead, and shifted the plane, in order to ensure that the hero was slain and unable to return. Of course, doing this resulted in a huge blowback of necrotic energy, that ended up creating the mournland- this can be the case even if their battle took place nowhere near cyre or at a different time. After all, we're talking about hugely powerful magics. It's also possible some idiot in cyre realised what had happened an attempted to replicate the spell, causing the 'spillover' that created the mournland. Either way, the result is the same.
Now the heroes can quest for the final artifact pretty soon, and once they do, it's about trying to move that plane back into alignement. As they work on this, they start to learn about the instability of the planes, and at the end of this process, possibly while comunicating with the dead hero they discover the truth- that shifting the plane and resurecting the hero will cause the mournlands to expand and fluctuate, at a dramatic rate.
With the mournland linked to this plane, any attempts to move the plane will cause wild fluctuations in it's borders, and that will cause terrible damage to the world.
The hero themself should refuse to return because of this. They're linked to this curse and the mournland, and can't in good conscience allow the zone to expand. Later on (in epic) the pcs could repair the damage, but right now, it would be madness to meddle in such forces.
So instead, the hero offers to train the pcs, teach them what they know about their foe and his servants, and generally act in a support role. However, they would also emphasise the new status quo of the paragon tier. You can literally have the hero challenge the pcs and tell them that it's up to them now- that their decisions and choices and ambitious will shape the world, and that they have to take responsibility for that.
The thing is, I don't see enough there for a whole TIER?
There wil be plenty of content if you work with the players, and move them into the driver's seat.