When a group of nine or more lantern archons are overwhelmed, they might use their gestalt ability to form a whirling globe and buy time for their allies. In such dire situations, a shield archon can teleport itself to take the place of the gestalt. However, in rare circumstances the lantern archon gestalt and the shield archon instead fuse in a flash of light and create a crater with a nascent bastion archon at the centre. The new bastion archon can fight but cannot move until it fully forms its body from the stone of Heaven.
Bastion archons rarely move even after gaining the ability to do so, preferring to defend the crater where it was created. Convincing a bastion archon to move is almost impossible, although in some rare cases they have served as mobile bases for other archons during a large crusade into Hell, Abaddon, or the Abyss. If a bastion archon sees a balor, it will cleave its way through demons to fight the balor to the death.
Given a choice to pursue enemies or tend to wounded allies, a bastion archon almost always chooses the latter. If a bastion archon is destroyed, it releases an explosion of light that heals its allies and consecrates the ground around it, which often ends up being considered a sacred place of remembrance.
In the Great Beyond
The bastion archons' dedication to protecting their charges has reached proverbial status in Heaven, so that "trying to budge a bastion" has become a way to refer to attempting to perform an impossible task.
An ancient bastion archon known as Anvil Fist patrols the deepest caverns of the Forgeheart to guard against invasions from the Abyss. It has recently begun to behave erratically, secluding itself in empty tunnels for days and only answering in vague aphorisms when asked about its behavior. This has led to worry that influences from the Abyss have corrupted to archon, while others speculate that Anvil Fist may be nearing a metamorphosis into something akin to a celestial equivalent of an infernal duke or balor lord.