From Halopedia, the Halo wiki
Operation: TENDRIL was a UNSC operation. Not much is known about this operation, other than that Dr. Catherine Halsey knew something about it due to the fact that it is mentioned in her journal. Based on the context in which it is mentioned, it is likely that the operation is related to the SPARTAN-II augmentation procedures.
List of appearances
- Halo: Reach
- Dr. Halsey's personal journal (First mentioned)