I would make like an undead character (WarCraft 3? The Undead....Like the Lich Hero)and these would be the bonuses:
Conjuration 15
Destruction 10
Alteration 10
Blunt Weapon 5
Illusion 5
!REMEMBER! The skills points have to add up to 45 like all the other races....
...and magicka = 10.0 x INT
They would have a increase in Intelligence and Willpower, but their Personality would start at 10 because everyone is afraid of this race, they run away when they see them, but creatures just attack, but their disposition with other people in this race would always at least be 60. And their Speed would start at 30 because they don't actually have legs or feet. And since people run away, this race has its own city underground which can be accesed by a trap door at these places:
Meldor, Armorer, Balmora
Halfway Tavern, Pelagiad
End of the world, Dagon Fel
Dirty Muriels Cornerclub, Sadrith Mora
Under Skaar, Ald'ruhn
The little prison, Arvs-Drelen, Gnisis
Underworks, Foreign Quarter
And their "Underworld" would also have 3 Great Houses, But only 12 main cities, 4 for each house. The houses would be called:
Great House Madoch (warriors)
Great House Marlo (theives)
Great House Mentrith (mages)
But the houses wouldn't be rivals, they would stick together, but they are just there so everyone can feel in their place, also everyone in their houses would like them with a disposition of 100, all the time.
The missions would concern destroying the world above, but you wouldn't literally destroy it, you would just trick each house into getting really mad with each other and causeing war with each other, and the mages guild would fight Telvanni, and Morag Tong would fight the Dark Brotherhood....like re-awaken their hates for each other.
But incase you did want to go up there into the other cities, when you first visit the Underworld, you will have a home givin to you in the middle of nowhere, somewhere in the Red Mountain Region, where there would be a ring, which you could use to make you look like a living person, you choose the race, but remember, dont wear it into the Underworld because the Undead race will attack anyone not of their race, and when in living state, you wouldn't be allowed to wear enchanted pants, skirts or shoes, and you not allowed to wear greaves or boots....because if you do, you be unable to move, like you were paralyzed.
But with the ring you could still do the Main quest and all the other guilds, but you will always a home in the Underworld.
But in the main quest I would make it possible to join Dagoth ur, and you two would literally raise hell on earth, and all the other cities would send armies to stop you but you easily kill them, and when your in you real state, peasents would run away from you, whereas stronger people would attack e.g guards....
Also remember that there are dungeons in the Underworld where you should go to get treasures.... and one more thing, there would be a main quest which would be to bring the Undead together, and start their rivalry again with the Hugh Grants,..uh, I mean Imperials, and you would enslave them etc.
So lets go over this again...
-Nice Skill Bonuses.
-HUGE Magika Boost.
-Low PER and SPD, but high INT and WIL.
-Can't wear shoes, boots, greaves, pants or skirts because you are like floating.
-Ring to make you look like a living person.
-Another ring which you get during the "Main Quest 2" which has a spell to posses someone for 600 secs.
-A house in red mountain.
-Nice huge Underworld, Undead Capital.
-3 new Houses that are NOT rivals.
-A cool 'Lich' like character, just that you dont have legs but you have this permanent skirt thing... but you hve to mix good with the bad...
-LOADS of new quests.
-Different types of architecture for each house's cities.
-Annoying thing of not wearing leg stuff, but again, mix the good with the bad....
Was this a good enough idea?
Critisim is welcome....