I do love these challenge ideas that fellow vikings come up with. I did something similar where I progress up to as far as I can without defeating a boss. The limit is silver age gear, it seems so far, unless I find another way. I dig the idea and you are right you do get to stock pile a bunch of stuff which can be helpful for the next step. Also gives you a chance to really just kinda enjoy the biome a little more too I think. A solid tip that might help you out before you take out the elder for swamp.

You can use a chair to get through the Iron Gates on the sunken temples. Its an odd master key so to speak. Place the chair facing the door and as close/into the iron gate that you can, its usually about half in half out. Take a seat and move forward and should pop you right in, if not give it a couple of more tries before moving the chair to try a better spot. Basically, bugging through the gate ;)

This little trick makes moving from the swamp to the mountains a much more pleasurable experience.

The guide that John above posted is pretty solid and helpful. I typically use the Troll as my employee of the month and I upgrade that stag hammer for longer durability when pounding around. As for the mountain biome you don't need a huge mountain just one tall enough that has obsidian and eggs on it.

I play permadeath and was able to conquer this new update with a new start at 216 days. Roughly at 100 days before I tackled all the bosses but the new Mistlands. No record by anymeans, but haven't tried the no-map or no-portal which could be a nice added excitement/fustration depending on whats going down. Oddly during the whole 100 days or so before I slayed the final boss I got only stir the cauldrons, about 8 of them. Weirdest event RNG.

Happy adventuring, SKAL!!!!