In order to complete this challenge, a Vault Hunter must travel to the northeast corner of the Caustic Caverns, where Blue is found, stopping at the furthest of the connected islands. The next step is to cross the ooze north to a lone island with a dead tree on it. This can easily be done with high level characters. Characters will need at least 8,000 Shields/Heath total or a proper skill selection to survive the crossing (the caustic slime deals the same damage in both Normal and True Vault Hunter Mode). Salvador can easily cross it while Gunzerking with Hard to Kill and Ain't Got Time to Bleed, both from the Brawn skill tree and fully unlocked by level 15. Deathtrap can assist Gaige or her teammates in crossing with Buck Up restoring shields.