Porta

The Porta is a sphincter-like orifice embedded in the floors and walls of Flood hives that act as the Flood analog to doorways. Portas were sighted in the Flood-infested High Charity.

Trivia

 * The Porta will only open for the Master Chief and not any of the Pure Forms or Infection Forms.
 * The "Porta" was recently parodied in VG cats #240, "...gross"