D&D longterm?

Near the village of Sunnydale, in the forests there is an old remnant of a bygone empire in the form of a road, over grown and in general disrepair.  But, it is also clearly more advanced than the roads of the nascent kingdom.  Where the latter is a dirt road the former is made of stone slabs, the later winds to its location, the former runs straight for stretches of time.  The haphazard placement of farms and villages is comfortable, but should it be explored the old road has regular and predictable stops along the way and at the ends the ruins of fallen cities, or their remaints.  One ends in a massive crater with shear glass like sides, perfectly circular.  The other ends in an overgrown riot with ancient buildings in groves of trees.  There are fountains that still work and sewers that are still conected and clear.  The fountains have a barrier that only lets residents of the city claim its water.  The water is fresh and provides health benefits to imbibers, but only if they drink from the fountain.  There is a community of kobolds and goblins here that patrols the area attacking anyone within fifty kilometers.  They bring the spoils to their queen, whom they worship.  They drink from the fountain as often as they can and so all members of the groups are about a foot taller than average and have an extra hit dice, in addition they are twice as fecund, wish is especially good since their queen will often dine on them if they fail to bring her wealth or better options for food.  Their queen is an ancient Green Dragon, and resides in the audience chamber of the palace along with one of the city's fountains.  The dragon is so large that if she were to try to vacate the room she would bring the entire castle down in the attempt leaving her unharmed, but burying her treasure.  If this happens she will be very irate and completely undamaged.  If the characters should venture in this location after battling the big goblins and the big Kobolds that have no treasure and discover the palace allow them to see the lazy flicking tail emerging from the doorway.  If they do not retreat immeadiately proceed with all intelligence.  The players might figure a way into the treasure hoarde, but if they fail the the dragon will capture some or all of the characters and hold them ransom, forcing the other characters to bring her more treasure provided that they are polite and respectful.  The dragon is Lawful Evil and will abide by her agreements.  In her hoarde, which she will proudly show off includes magical items that appeal to some of the character types.  She might be persuaded to part with those items if they present her with something more to her liking. She will be wearing magical items that she has.  In addition, she is an accomplished Illusionist and uses her powers to effect.  She knows that she is not the only power in the city and that she does not have the reach to establish total control, but maybe the Player Characters will help her.  There is a massive dungeon complex in the city out of her immeadiate range.  And there are three enemies there that hold her power in check.  A Mindflayer colony, a beholder and a powerful group of Aboleth.  All hold a number of NPC races hostage and is using their safety to manipulate the race.  

The city:  the city is large.  Very large.  The entirety of Greysteel can fit into one block, those that have been to Jarda would feel that the city would dwarf it like a mouse beside an elephant.  It is thirty kilometers in diameter and a perfect circle.  The walls are purely ceremonial, as there are no battlements and siege equipment, smooth and unblemished, only covered with the growth of thousands of years of vines that obscures a mosaic pattern which is purely aesthetically pleasing.  The buildings have a genuinely alien feel; everything is slightly off: the steps are a little too large for human or elf kind, like everything is made for a race who averages 6'6", where writing appears it is alien.  Any PC with a knowledges of more than six languages two must be of a humanoid language like Orcish an Gnollish has a chance to figure it out DC 25 on intelligence check, but only after hearing the language spoken.  This City is the first city of the Orcs.  It is built of imperishable concrete mixed with a low level electrostatic field, powered by nano solar generators imbedded in the surface. Many of the buildings on the periphery of the city still have working facilities including some working voice interfaces.  Anyone with good architectural and weather knowledge will recognize that many streets are laid out to catch the sunrise and sunsets of the solstices and equinoxes.  

There is also evidence that the city was witness to a great cataclysm in the very deep past.  The buildings on the eastern side have been blown over like trees in a great wind the ones on the western side are all damaged but less so than the ones to the east.  Many of the towers are resting on others like giant dominoes that were placed a little too close to topple over.  The towers in the east were destroyed, like a tree turned into toothpicks and left to scatter.  The toppled towers are most impressive; there is only one at is intact and it is in the west, smaller than the ones in the center by half, but still a five hundred meters tall.      

The Dragon and its lair:  in the center of the city rises a large temple dedicated to the Suns the temple is lower than many of the buildings nearby, the large boulevard between it and the city is littered with the corpses of the buildings.  This building rises like a cathedral made of crystal and white stone.  It is only two hundred meters tall and inside it is an airy shell, egg shaped internally and sculpted magnificently outwardly.  Large trees have sprouted out of the ground around the region, growing on the fallen buildings, in them, and around.  Within the dragon sits surrounded by its hoard which includes coins from empires that risen and fallen in the shadow of this sleeping city.  The dragon controls the north and the south of the city with its minions. It has grown to fill its home and cannot leave it unless she rips it apart, which she will do as a last resort.  She is a level 12 sorcerer, so that makes her a CR25 encounter (75000xp) she has managed to acquire a massive hoard which includes many magic items.  She will use these magical items to procure the services of the adventurers.  To clean out the interlopers in the rest of the city. There are three that she is aware of and her subjects are not up to the task, which should tip off the characters.  She will claim truthfully that she is very comfortable where she is right now, and her enemies are not stupid enough to come to her, so, she must find someone to take the battle to them.  She will be bargained with but she will not be trifled with.  She can tell when people are lying to her.  She will also send them to the targets she believes that they can actually win against like the Mindflayer colony and the Aboleth before the Death Tyrant.  When they are successful she will be generous in her rewards. She has many intelligent weapons in her possession, which she holds conversations with, she calls them her court.  She will never give up the Dragon Slayer's she has acquired.  She might offer them aid by giving them salvaged Orcish Disrupters, treat as wands of disintegration with 1d10 charges. 

The Beholder and its lair:  the intact tower is the back door for the Tyrant.  It can rise the shaft and exit the 500m after 7 minutes of flight.  The only way up without flight means fighting up the towers 250 levels.  There are about 700 zombies in this tower including 10 beholder Zombies, three guarding the top most level.  Should they smartly attack from the top the other beholder zombies will converge from the top at their best speed, which is one per minute. The best direction of attack is from below, where they merely need to avoid patrols of undead that include twenty zombies lead by an ogre zombie, the zombies include all the other factions troops.  The Death Tyrant has no hope of defeating the Dragon, but has the best chance of doing so, so it waits patiently gaining forces slowly.  It has blocked off all the entrances to its area with disintegration rays so that there is only one front door and one back door.  If hard pressed, it will recall all the powerful zombies and make a kill zone at the bottom of the tower.

The Illithid and its community:  located at the Orery is the entrance to the community,  there are three Arcanists guarding the entrance, they are actually using the device to attempt to figure out the best time to go forth in strength.  They are outcasts, but have determined that if they can discover the best time to go forth, they will be allowed to breed.  The three Arcanists control a group of nine Gith warriors.  These are remnants from the Illithid Wars.  Deeper in the caverns are a host of Kuo-Toa.  The Elder Brain resides in a cluster of 24 Mindflayers.  There are many servants located in the depths.  Intellect Devourers range around the Orery and the building obscures a passage down to the depths below the sewer and subterranean living areas there are pitched battles in this part of the underground between the forces of the Dragons and the two Underdark Players.  Each Mind Flayer controls Twenty-four CR worth of creatures, plus their leaders, such a as 12 ogres and an Ogre leader, 12 quaggoths, 98 grimlocks, 8 gith, 98 kuo-toans, or 98 troglodytes.   There are three large communities of Kuo-Toans with leaders numbering over five hundred, same for Grimlocks and troglodytes.  There are 24 ogres and 24 quaggoths spaced to keep the three armies focused.  The 40 gith are there too.  If the players should sneak past and kill the Elder Brain, this break the hold on two thirds of the inhabitants and they would rebel, possibly killing their controllers.  But any sighting of the characters would count as sightings by the whole.  The Dragon would like this option the best as it would be likely that she could gain some of the better warriors herself.  There is one Intellect Devour for every Mind Flayer.

The Aboleth and its communal lair:  the Aboleth have been probing this city for ages.  They have allied with a city of Duergar after they enslaved their enemies the Svirfneblin.  This means that they have a force of about a thousand slaves and allies.  They are pressing the Illithids from below and pushing into the sewers of the city.  The gnomes have summoned many Xorn and Elementals to aid them at the Aboleth's prompting.  They are not trying to take over this area, but they are getting information on the area.  They will take all their forces with them if threatened by a strong force.  The Duergar are intent on destroying the Illithids.  If this should happen they will gathers up the Kuo-Toans and the other Underdark residents plus as many of the other races and enslave them, nine per day.  They will retreat to the depths.  They will first try to lure a PC to their doom and abduct them to their master lair, the deep lake to the north, the crater lake, it is 15 kms deep and there are 10 more Aboleth there.