Tykos 30 was an organic tracking device. It has a similar appearance to the yellow liquid "blood plasma." One Marine described to Ruwan Ackerson who was injected with the substance that they "can track ya to Mars." The UNSC believed that the Covenant were not aware of its use, and were unable to track the substance.[1] In reality, they could, but they misunderstood its function.
Sources
- ↑ Halo: Uprising, Issue #4 ("We can track you. They can't.")