Porta

A porta is a sphincter-like orifice embedded into the floors and walls of Flood hives that acts as the Flood analog to doorways. Portas were sighted in the Flood-infested High Charity and on the Flood dens.

The portas replace the doors in the original architecture of the Flood hive, because of the excessive growth of Flood growth pods in the area. Even though the Gravemind controls all Flood forms, it doesn't control the opening and closing of a porta. This is supported by the fact that during Master Chief John-117's raid on High Charity, the portas in front of him opens, despite the Gravemind's attempts to stop John's progress to save the AI construct Cortana.

Trivia

 * Portas are comprised of seven segments, and there are seven Portas on the campaign level Cortana.
 * The name "porta" probably comes from the Greek word porta (πόρτα), which means "door".
 * On the Halo 3 multiplayer map Isolation, there is one Porta. Sliding down a hole on the top part of the map will lead the player to slide down a tube. A Porta will open, leading into a Flood-infested cave.
 * There is a running joke among gamers that the Portas are the Gravemind's intestinal openings, due to their sphincter-like appearance.

List of appearances

 * Halo 3
 * Halo Wars