For the purposes of introducing a completely new player/someone unfamiliar with Sentinels lore to the game, I'd actually take the reverse approach: List the four Void Guard characters by their role/abilities, and then you can list The Sentinels as a "these four heroes working together."
Using a real comic example: Each member of the Fantastic 4 has <X> power and contributes <Y> as a character. The Fantastic 4 is them working together as a team.