Lead sulfide crystal
Lead sulfide crystals are a Cybertronian food product, and are apparently delicious when combined with savory mercury sauce and flavorful iron filings as garnish for a tasty snack. They are, of course, poisonous and quite inedible for humans. The crystals found on Femax emit a greenish glow.
Lead sulfide additive appears to act as a remedy for some Transformers. Lightspeed must take some with his fuel or break out with a rust rash and other troubling symptoms.
Fiction
[edit]Marvel The Transformers comics
[edit]Cloudburst and Landmine were looking for the lead sulfide crystals to try and stave off their incoming consumption by the Mecannibals. This is because, logically, their metal bodies would taste super bland without the proper seasoning of these crystals, so if they go and get the seasoning, then they'll earn their freedom and not get eaten! Much like how a human being will be more satisfied with a cup of pepper in place of a steak dinner, after all.
The situation got more complicated when the only place to find the lead sulfide crystals was on the planet Femax. Using Pretender technology to facilitate diplomatic relations, Cloudburst got swept up in a royal romance with the First One, the leader of the planet. After finding out he was not actually a male and in reality an alien robot, she got really embarrassed and cut off his head, which is a completely reasonable reaction.
In the end Landmine managed to negotiate properly and the First One realized her mistake, granting the two of them their lead sulfide crystals with no further fuss (and also returning Cloudburst's head). These crystals had a dashing adventure involving betrayal and return, and presumably after Cloudburst and Landmine returned to the Ark, they were gobbled up by the Mecannibals and digested. Recipe for Disaster!