Ok, after one beats the main quest, is one supposed to just run around and do other ones? What if....one has beaten all the quests they can possibly find? Is there some other big important thing to do, or does the character just get old and die, or do you just raid caves forever? If...someone could help me out, that would be cool. All the guild/group quests: check. Arena: check. Main quest: check. Wandering around looking for inns and towns: check. What else is there?!
Um... get all the doomstone powers... the ones you get as your infamy/fame goes up...
Pretty sure you have to have a total of 70 to get the highest one. When you get them all, with potions, you should have around 700-900 magicka if you are maxed... That alone gives me all KINDS of ideas...
Make your own spells....
Make a new character and play using a different style. Try being "evil" or "good." Try kill a Lich in one hit... Try kill a Lich with a silver dagger...
Um... try beat all the quests before level 20, try max your char out to level 50-52 (the highest level possible with a specially created character is 53-54 or something like that, and you have to really mess up your skills)
Talk to everyone......
When all this fails...
DOWNLOAD MODS!! Mods are the BEST!!! Because of the WONDERFUL modders, Oblivion will NEVER END!! YAY!
Some ideas...
Cadaver
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You're such an inspiration for the ways that I will never ever choose to be.... (Maynard James Keenan - Judith)
Well once all quests are completed I think the game is designed for you to simply stop playing that character and start a new one. Try one pure evil, or one pure good, only joining the evil/good factions. Should be an interesting change instead of running around doing 'nothing'. See how you get along if you have 100 infamy points and 0 fame points and everyone's attacking you... (if that is possible).
Anyway I envy you for wanting to play the game for so long. I got fed up even before I did all the quests. Hope I'll get the urge to play again soon though.