It's pretty hard, yeah. You need to get lucky with the restore cells/gems, as well as have the high shield as high as possible. I did my usual strat of using sanguine signet + snow boots until lava, then switched to winterheart and magmawalker, using one mageflare rune every seven depth to do optimal traversal. At the obsidian I swapped out winterheart and made it with 2 health to spare after several attempts. It's probably the hardest still doable challenge in the game, unlike all turtles beside Griddle in hard mode