If you want to make the game truly difficult, play "dead is dead" (no reloading when you die, unless you died due to a game glitch), turn the difficulty slider all the way to the right, stick with your jail clothes, only use the starter spells, and don't loot anything.
Evar.
That'd probably fall under "so difficult as to be literally impossible" however. Still, those can give you an idea about how to increase the challenge yourself.
- I'd like to play a mage character, but am hoping to make them a bit of a glass cannon mage.
I'd argue that all mages are pretty much glass cannons. Oblivion magic can be very overpowered, especially once you learn how to create the really effective custom spells. Wearing armour reduces your spell effectiveness, so it's common to just wear robes or plain clothes instead so your spells hit with their full effect; it's mainly noticeable with Illusion spells, like a Demoralize up to level 10. If you're wearing armour, your spell effectiveness will be more like 90% instead of 100%, which means if you cast that spell on something that's level 10, it probably won't take. It'll also reduce damage caused, but that can be harder to notice, especially with custom spells and multiple hits.
And instead of wearing armour, a mage will usually enchant their outfit with, and cast, Shield or elemental Shield spells to provide protection. Spell Absorption and Reflect and Resist spells also help reduce damage. At some point, you'll probably want to monitor the use of those spells, to prevent the godly character that will often result.
- Should I stop leveling at a certain point? I don't totally understand the leveling system, but what I'd like to achieve is a point where the toughest creatures/NPCs/enemies will spawn, and at the same time I won't be too powerful. From what little I've read I'm guessing I should stop leveling around 15 to 20???
When you get ten increases to your Major skills, you'll level up. The only way to control leveling without mods is to pick 7 skills you'll only use until a certain level. Once all Major skills are maxed, you'll stop leveling, and normally that happens between 50-65 IIRC.
Leveling to around 30 is pretty good, that ensures that all possible enemies will have appeared (many don't appear until you reach a certain level), and, if you care about the quality of quest rewards, the best levels should be available. The world levels up with you too, so for the most part, you won't be running around one-shotting everything. Mudcrabs, probably, but find yourself some goblin warlords and try it.
- It sounds like it would be a bit broken if I tried to make a Mage character that focuses on Chameleon or Invisibility and Summoning. Is that accurate? In the vein of a glass cannon mage how would it be to focus on invisibility or chameleon (I don't actually know what chameleon does) plus Destruction? I would imagine I could eventually become powerful enough to wipe out one enemy but have to use some trickness to take on multiple enemies. This is the kind of scenario I'm looking for.
Summon + Invisibility is just one of several tricks to surviving encounters, so no, it's not something that'd be "broken." Doing it all the time, yeah, it could get boring, but when things are about to go terribly, horribly wrong, it can save your life.
Just play around with all the different schools and see which spells you prefer to use. For example, there's a lot more to Illusion than Invisibility and Chameleon, and with Conjuration, you can turn away the undead (like to thin a crowd to a more manageable size), or conjure specific creatures for specific fights. There'll be lots of reasons to use most of the available spells, so try them all and see how they'll fit into your playstyle.
Same with fighting a single enemy versus multiple enemies -- there are different tricks to controlling crowds and utilizing AoE.
- If going the glass cannon mage would be a good route, how would a Breton with the Apprentice sign be? I'm interested in the Apprentice sign because I read it gives you access to the Weakness to Magic when you make spells. It also sounds like you can acheive that without the Apprentice sign, by doing the appropriate quests. I very much like the idea of create my own spells and "Spell Stacking." I understand Spell Stacking can be quite powerful, but again I'm hoping I can temper my overall power with a "glass cannon" type of character.
Breton would be a good choice for the Apprentice sign, due to their natural resistance to magicka, and enchantments can be made and found to compensate for the other 50% weakness. You can buy the spell though, so Atronach would be a good choice just for the extra magicka bonus, and learning how to cope with magicka not regenerating would probably be an acceptable challenge. In fact, a lot of people prefer that sign (I'm not one of them, Mage is fine for me).
- I'm fully willing to invest heavily in social skills, or social spells if it'll add to the overall quality of the role playing experience. If it will just making getting info overly easy I'd rather avoid that kind of thing.
Meh, Speechcraft really doesn't provide much benefit overall. There are times when you'll need to increase someone's disposition towards you in order to retrieve information for a quest, but that can be achieved with a Charm spell. If you want to be chatty, you can without worrying about that skill, because it only applies when you do the http://www.youtube.com/watch?v=rWW0YY6OYTM (the link shows a video of how the minigame works, so don't click if you don't wanna know yet). Also, increasing a vendor's disposition will let you haggle with them more, for better deals. Your Mercantile skill will increase on its own as you buy and sell goods, and it's another skill that isn't necessary to work on. Past Journeyman level (which isn't too difficult to reach just by selling stuff), the perks just give the merchants more gold for you to take, and by the time they're activated, you won't usually need them much.
- As opposed to a glass cannon style mage, I'd probably really enjoy some kind of hybrid type character. Perhaps a mage style assassin who specializes in poisons and destruction magic? I'm not sure if something like that is viable.
Oh yes, definitely. There are 21 skills to use, and it's completely up to you how you use them. There are several default builds that can give you an idea of the possibilities, but keep in mind that just because a skill isn't a Major doesn't mean you can't use it. Part of the appeal of TES is the ability to create a wide variety of characters -- and roleplaying will have a big impact on that, because your character will probably only use certain skills anyway.
- Should I avoid conjuring altogether? I like conjuring the skeletons, but I don't want to just become invisible, conjure a Balrog (any kind of powerful summoned creature) and wipe out anything.
Totally up to you. Most summoned creatures are tough, but you'll only be able to conjure them for well under a minute (a custom 2-minute spell costs an outrageous amount of magicka), so they simply won't be around long enough to tear up the place. However, increasing the difficulty increases their strength too, so although you'll be taking more damage and dealing less, they'll be right in line with the enemies in that respect.
Also, conjuring critters doesn't mean you have to go invisible too. There are several reason why a summon can be useful, like if you're indoors and you want something big to block exits and prevent runners from escaping, or a runner has escaped and you want something that can catch them and continue the fight while you can catch up. Clannfears are great for that. It's also another way to fight multiple enemies -- while you're dealing with the guys over here, your atronach can be fighting the ones in that corner over there. It's also amusing to watch melee fighters try to fight a wraith, because their weapons usually won't cause any damage, so the wraith can continue softening them up for you.
Regarding http://www.uesp.net/wiki/Shivering:Shivering_Isles -- the basic PS3 Oblivion game will include http://www.uesp.net/wiki/Oblivion:Knights_of_the_Nine, while Game of the Year will also have SI, the only expansion. The rest of the http://www.uesp.net/wiki/Oblivion:Official_Plug-ins isn't available on the PS3, since development was finished well before the PS3 was released. Both of those can be done at any time you want, and KotN is especially good to do early on for goodly characters (paladins, crusaders and the like).
SI is also leveled with you, so you can enter it at any time, just like the rest of Cyrodiil (although you'll need to do a few things initially to gain access to the whole island). And as mentioned, the creatures there are a bit tougher than what you meet in Cyrodiil.
Also, the most important thing to remember is that Oblivion is meant to be experienced, not beaten. There's no "Game Over" screen, you just keep playing until you decide to stop. There are lots of things to do, and there's even a 100% completion page at the UESP, but if you're into roleplaying, you'll probably want to experiment with several different kinds of characters who'll each do certain parts of the game, or come up with really good reasons to do some of the things that contradict each other, like the Dark Brotherhood and KotN.