I think it would make more sense if players were made to progress through the mountain biome first and then the swamp afterwards. First I will explain what changes should be made and then go into why I think this is a good idea.
Changes:
- Elder now drops the wishbone, which is renamed to divining rod.
- Swap the metals: mountains now contain iron, swamp crypts contain silver.
- Change frost resist potion to be craftable without swamp materials, change wolf cape to require iron instead of silver.
- Nerf mountain mobs, buff swamp mobs (except poison) so that they fit in the new progression.
- Moder now drops the swamp key, renamed silver key.
- Bonemass now drops the item required for the artisan table, renamed to Tesseract.
- Optional: change frost/poison arrows to require ancient bark.
Why make these changes?
- Iron is needed in much higher quantities than silver, so it would be much easier to farm from the mountain rather than relying on the random generation of swamp crypts. Thematically, silver makes more sense to be placed in crypts to honor the dead since it is a valuable metal. It also makes sense that a dragon would swallow the silver key since they like shinies.
- The swamp is already considered harder than the mountains by many players so it wouldn't require much rebalancing.
- Mountains are much easier to find than swamps (due to the tall terrain silhouette). With Moder's power unlocked earlier, finding swamps (especially a good one with lots of crypts) and ferrying metal on boats would be much easier.
- Bonemass's power isn't really required until plains anyways and is of little use in the mountains vs drakes/Moder. Bonemass dropping the Tesseract to unlock new crafting would feel cooler than dragon tears.
- Frostner/frost arrows would unlock in the swamp, which would entice players to make them as they are ideal against Bonemass/swamp enemies. This would help guide some players that are struggling with swamp to use the correct tools. Some players already skip to the mountain for frost arrows to use vs the boss anyways so this would just reinforce that behavior.
- With these changes, the stonecutter will unlock after getting iron in the mountains. Guess what contains LOTS AND LOTS OF STONE?