From Halopedia, the Halo wiki
The player spawns with an SMG and a sniper rifle, but no enemies populate the space. The art in this level was likely created by Paul Russel. When playing, the level has a low framerate. This version of the level seems to match up with early storyboards for an early draft of this mission, and unused scripts found in the Halo 2 Mod Tools.
Cut scripts indicate that this early revision of deltatemple was to have stealth mechanics such as a work-shift change for Covenant patrols and dialogue with Cortana informing the Chief that if he's not quick, the Covenant patrols may find the dead bodies of guards he has killed. Additional dialogue for if the player did choose to go loud is also present. A new type of enemy was to be used in the level, called a "Comm Grunt" which would have alerted its allies in certain situations.
Curiously, when entering the multiplayer lobby of this build, deltatemple is available for play as a multiplayer map. In the menu, the level's preview images are those of early builds of the final level Ascension.
The early storyboards depict an early version of deltatemple in which the In Amber Clad exits slipspace above the ring and engages in a space battle with two Covenant cruisers, before proceeding to drop Master Chief alone onto the ring. The Chief exits his drop pod armed with a pistol, though once he's sure the area is clear he switches to a sniper rifle.
A number of the level's ideas made their way into the retail version of the game. The basic idea of hunting down and killing a Prophet ended up becoming the narrative basis for the levels Delta Halo and Regret. More specific concepts such as the underwater halls made it in as well. Even entire lines like "You always bring me to such nice places." from Cortana made it wholesale into the retail version of Delta Halo.
The following dialogue and sequence of events are transcribed from remaining files in the Halo 2 Mod Tools.
The level starts.
The player approaches a complex.
The player witnesses a guard shift change or possibly the Changing of the Guard.
The player comes across some Unggoy playing Hide 'n Seek.
The player sees a Prophet delivering a speech.
Cortana translates the speech.
While on a central platform.
The player reaches a tower with an elevator in it.
If the player delays calling the elevator.
When the player has reached an underwater hallway.
When the player reaches an underwater chamber
The player reaches a second elevator.
A view of the temple is seen.
A dropship arrives and begins dropping off various Covenant elements.
The player walks past a craft.
The player enters the temple.
Once the player kills the target Prophet.
The player returns to the shuttlecraft they spotted earlier.
This dialogue is considered "Misc." Given the context provided, it was likely to be used for gameplay sequences.
The player spots a "Comm Grunt".
When the player enters an area that is not alerted
When the player has been detected