- "Because of its speed and luxury the Pious Inquisitor has become an irresistible prize during these dark times."
- — Map Description
The map takes place inside the Pious Inquisitor, like its predecessor. Outside of the map the player can see a fleet of Assault Carriers and CCS-Class Battlecruisers, all heading slowly for an unknown gas giant. On the opposite side of the map another planet or a moon of the gas giant can be easily made out. A distant star illuminates the planets and a massive orange nebula surrounds the Sun.
The interior of the ship is built off of the same "blue prints" as Midship was. The only physical difference is that doorways have been added for aesthetic reasons. The interior is typical of Covenant design. With dark pink walls and surfaces as well as gray colored floors and walkways.
It is located on one of the blue ledges beside the Sword platform. If you enter Monitor Mode while on the sword platform, and fly up and look to the right, the skull should be disturbingly staring at you.
- It is wise to avoid rushing for the sword, largely because you are in full view of both bases and the ramps. Instead attempt to pick off the early rushers before grabbing the weapon.
- Plasma grenades are abundant on this map, use them frequently.
- It is optional to stick to the outer parts of the map, as the center is barely covered and susceptible to grenade throws,
- Players start with plasma grenades, which can counter the sword carrier if you stick them as they lunge at you. Be careful when doing this, because the subsequent explosion may kill both of you if the attacker gets close enough.
- Once again there are curved and slanted walls around the map, use them to angle in grenades.
On Heretic, there are two achievements available to get, the first being the hidden Skull which will award you 25 Gamerpoints, and the second being Blades of Fury, the requirements of which being to get a Sword Spree on Heretic (ranked or social), and will also award you 25 gamerscore.
- The Assault Carriers seen outside the view ports have a Marathon symbol on each side. Another Marathon reference.
- Heretic is the fifth remake/reimagination in Halo 3 ; the others being Last Resort, a remake of Zanzibar, Blackout a remake of Lockout, Avalanche, a remake of Sidewinder and Cold Storage, a remake of Chill Out.
- In Bungie.net's Halo 3: ODST Pre-Pax Podcast, Bungie level developers stated that an event may occur on Heretic in which, after 40 to 44 hours of playing on the map, the Pious Inquisitor will arrive at Assembly. However, this Easter Egg is still questionable since it is unknown if the "Easter Egg" was legitimate or a subtle joke. Bungie Podcast: 09/03/09
- The ships seen outside the Pious Inquisitor only move back and forth, staying in place, adding greater question to the Easter Egg claimed to exist.
- Just like Midship, there is a planet and a moon outside the windows.
- Bungie has stated that Heretic was built off of the exact same foundations as Midship.
- There are Marathon symbols reflecting off of the curved surfaces inside the ship.
- It is possible that the fleet is either Regret's fleet from Halo 2 or the Covenant Separatists returning to their home planets at the end of Halo 3.
- Heretic is the only map in Halo 3 to have you start with plasma grenades.
- The large sandy moon seen outside the map could be where Sandbox is set, and the ringed gas giant could be the same planet seen from Sandbox's surface.