Heretics are good for little more than manual labor. Chaos puts these wretches to work doing everything from constructing field bases and laying down defenses, to performing repair and maintenance. Using ancient incantations, they summon all building materials directly from the warp.
The Heretic is used to construct and repair Chaos buildings, as well as repairing damaged vehicles. Like all builders, they should be assigned to build as many Listening Posts on all captured points as they can to strengthen the economy.
One of the useful tools the Heretic brings to a Chaos player's arsenal is Forced Labour. It is an ability which allows a Heretic to construct buildings at the fastest rate in the game. However, it deals a constant source of damage to the Heretic, and can eventually bring about their death, as there is no warning feature built into the ability. The Heretic is willing to give its life to the Ruinous Powers, such is its devotion. This requires a player to carefully evaluate when and where to use the Heretic's ability. If used in a dangerous area, an enemy could destroy the Heretic in its weakened state, possibly before a desired building is created. However, neglecting to use it can set a player behind the crucial curve of battle. A skilled tactician knows that all advantages must be harnessed to achieve victory.
When using two workers simultaneously, each works at 75% of his normal speed producing a 150% build rate. Using Forced Labour on one Heretic produces a build rate of 300%. With two Heretics and one under Forced Labour the build rate is 75% * 3 + 75% = 300%. This means adding another Heretic to a job that already has a Heretic working under Forced Labour does not change the build rate. Two Forced Labour Heretics gives 75% * 3 + 75% * 3 = 450% build rate. This will get the job done faster than any other race can match (just 12.7 s for a Chaos Temple) but will probably require the replacement of both Heretics.
Heretic uses the dark powers of the Chaos gods to repair damaged buildings or vehicles. Heretics repair at a rate of 15 hitpoints per second. Up to three Heretics can repair a single vehicle or building at a time.