Lak 'Vadamee was a member of the Vadam family, rulers of the powerful State of Vadam. He was old for a Sangheili and was an Elder of the Vadam lineage. He served as an adviser to Thel 'Vadam and was the one who taught Thel how to fight and use his reasoning skills from such a young age. He is known to have a relation to the Arbiter Thel 'Vadamee as they both have the same pre-fix of their name.
When Thel returned from his mission to the 23 Librae system with a promotion to a command in the newly formed Fleet of Particular Justice, he confided in Lak that he was confused about his old beliefs about the perceived omnipotence of the San 'Shyuum and the worthlessness of the humans. This confusion was caused by the small feud between Regret and Truth indirectly causing hundreds of thousands of Covenant deaths and his close encounter with Jai, and to a lesser extent, other humans who fought bravely. Thel was worried that his thoughts verged on being heretical. Lak reassured him that what heresy was depended on who was in power, citing the Sangheili-San 'Shyuum War as an example, before encouraging the newly promoted Supreme Commander to be optimistic and to triumph in his battles. This, coupled with recent events, may be a direct reason as to why Thel became noticeably less zealous later, ultimately turning against the Prophets.
Lak is known to have served in the Sangheili Military Forces as his name has the 'ee' suffix.
- Halo: The Cole Protocol (First appearance)