From Destinypedia, the Destiny wiki
Ma'adim Subterrane is a Lost Sector located in the Glacial Drifts area on Mars. The lost sector contains Red Legion troops in the cave but it's unknown what are they doing there. The boss here is Valus Dulurc.
- Uldren Sov's ship is located inside the cave.
- "Ma'adim" is "Mars" in Hebrew (מאדים).