Sierra-7D, also known as S-7D or simply 7D by his teammates, is a low-mid rank Combine grunt belonging to the Sierra-7 team.

S-7D has been in The Combine forces for approximately 2 years, first enlisting as a member of the City-15 Civil Protection. As a result of the civil unrest in the nearby City-14, S-7D was then reassigned to be stationed there, as a result of a staff shortage.

After several weeks of attempts to subdue the riots in C-14, some remaining low-ranking Combine humanoid units have been evacuated. As a result, S-7D has been given permission to relocate as well, under the condition that he was to receive a non-optional promotion to an infantry unit, later to be assigned to the City-17 Quarantine Zone.

Sierra-7D's augumentations are minor, indicating a lower middle rank of a standard Combine grunt. Unit S-7D possesses:

• Basic sincipital reinforcement plate - web-like metallic structure implanted into his skull, visible from his forehead
• Additional reinforcement plates - present in his right eye socket and nasal bridge
• Optic augumentation in place of his right eye
• Synthetic structures: dental
• Internal vital sign monitoring system
• IV/IM injection port

The unit is approximately 180 cm tall and is of a slightly bigger build than the average Combine grunt. S-7D's right eye is missing, in its place there are two optic-neural fibre cables that connect to his mask, without it, his vision is impaired. His eye color is blue.