In grizzlehiem, I've done every quest I can (besides the fishing one) and I still haven't unlocked ravenscar, hrundle fjord, and nidavellir. I still have the yardbird and lore of the runes quests, but I can't finish those without ravenscar. The quest finder says that there are no quests available too.
Savarstaad Pass: level 20 Vigrid Roughland: level 25 Mirkholm Keep: level 35 Nidavellir: level 40 Ravenscar: released immediately after you defeat Jotun (used to be level 45) Wintertusk: released immediately after you complete Ravenscar (used to be level 50)
So, at first guess I'm going to suppose you're under level 40. If that's the case, you just need to level up some and the rest will open up for you.
*Note that Wintertusk is theoretically available at level 40 ... but it is extremely difficult for most wizards to complete at such a low level. If you're going to solo that world, I'd advise waiting until at least level 48 before you attempt it. Having your level 48 spell will make Wintertusk much easier to survive.
Savarstaad Pass: level 20 Vigrid Roughland: level 25 Mirkholm Keep: level 35 Nidavellir: level 40 Ravenscar: released immediately after you defeat Jotun (used to be level 45) Wintertusk: released immediately after you complete Ravenscar (used to be level 50)
So, at first guess I'm going to suppose you're under level 40. If that's the case, you just need to level up some and the rest will open up for you.
*Note that Wintertusk is theoretically available at level 40 ... but it is extremely difficult for most wizards to complete at such a low level. If you're going to solo that world, I'd advise waiting until at least level 48 before you attempt it. Having your level 48 spell will make Wintertusk much easier to survive.