Tar???

The Tar (question mark?) is a resource gained from the tar pit in the Interred Citadel. It burns very slowly, making it useful as fuel. Austin did not tell the players this immediately, and thus insisted that they write it down with three question marks.
Marn attempted to draw four bottles of tar??? from the pit, one for each party member, although she experienced minor supplies fallout and found that her invisible ink was actually just an empty bottle. 
Pickman used her bottle to fuel her armor in Episode 31, dealing damage to Mabriella du Feza's two hair simulacra directly with a horrifying video game glitch. In Episode 32, Es traded hers and a wicker finger with Lye Lychen for half of his dynamite.