After you clear down the mountain path at the start of the fjords, there is another beach you can swim to (or fly almost to) with level 18/19 black ring members on it, behind some anti-dragon shields and defenses (which you can ignore in human form).
Once you start on the level 21 imps right away, summon your creature to help with the imps. You shouldn't have too much trouble with them (at least in small groups) at the same level. If you attack the imps with a bow from a distance (even without investing in ranger skills), you should at least be able to do some damage as they approach, and make it easier switching back to melee. Even if you just take one or two before you need retreat in order to heal (level 1 of the healing spell comes in handy, and would help conserve potions), that will mean an easier time for the next attack.
On Sentinel Island you can teleport to the shrine outside, jump up the rocks and run over to where there are no overhanging tree branches in order to change into a dragon (IIRC you may also be able to find a spot on the path down to transform, or jump off and turn into a dragon before you get too deep into the poison gas). There are probably a few remaining attackers, left when you automatically returned to the battle tower, as well as a few places you can now reach as a dragon. The quest to retrieve a book from a boat in a tree can be done now, but you might want to consider using the book yourself, rather than complete the quest.
You can also use your dragon stone to teleport to the throne room, and send your runners for ginseng (etc), malachite ore and diamonds to sell (if you don't need any other enchantment ingredients). Wait until they leave, then exit and return; once fully upgraded (talk to your trainer and enchanter) they should have a pretty good success rate, and you can do this repeatedly to build up alchemy and/or enchantment ingredients.
If you fly out over the water from the start of the fjords, you should see a bunker high in the mountains behind some anti-dragon shields and defenses. That is where you need to get to lower the barrier and disable the shields (there are a couple traders in there, as well, after they surrender).
You can either use a teleporter to get up there (the Camp Sentinel View teleporter, on the west side of the island in the middle of the channel, will bring you to Camp Eagle's Nest, where you can access the bunker) or it is also possible to fly above the anti-dragon shield and drop down in human form, if you find the right spot.
There is no rush to get to Aleroth. There are a couple of good traders there, but Zandalor will be fine until you are done with everything else; that quest is needed to get to the final section of the game. You need to find at least one of each of the 3 types of zeppelin parts (there are 3 of each type) and turn them in at the harbour to get the zeppelins running again. The pieces are predominantly in or near wyvern nests.
