I managed to reach Depth 430 twice using Nix but it wouldn't let me go deeper (into purple section)? There was the yellow stop sign indicator but I still had 21 stamina left. Really upsetting since I finally reached the end of the Magma zone after stacking 130 shield and lucking out on heals.
I was hoping Magmawalker Boots gave Burn immunity but it's only sideways. I ended up having to forge Winterheart accessory anyway since HP is tight for Nix and that Burn dmg can kill my run easily. Since Nix can't equip tools, once her shield breaks she's no longer protected from extra stamina loss.
Gilded Shift seems like an overpriced 100% collector's item. I think by the time you can afford it, it won't matter since you'll access Titanium before Diamond. You won't need to swap out a broken Gold Pickaxe anymore and you can just take the -5 stamina hit to swap to Magmawalker Boots. Basically there are more practical, stronger accessories.
Quartz income is pretty slow but I think that's intentional for the sake of pacing out Dojo upgrades/Accessory purchases/accumulating enough to win Jackpot in Slots(without resetting).
You can sell excess Copper and Coal later on but that's only really pity change from Slots rewards. It's a trap considering you unlock Smelting speed upgrade after maxing all the three Dojo stat upgrades, and Dwarven Bracer late-game which both require a ton of Copper.
Besides Diamonds, Ruby upgrades were the worst, probably on account of Amethyst/Emerald/Sapphire having more biomes to spawn in and also the Dojo upgrades skipping over the first two gems for the third type.
