The Templar Archives is an advanced Protoss tech building. The structure allows the Protoss to produce High Templars and Dark Templars from the Gateway. In addition, the Templar Archives allow the unlocking of level 2 and 3 ground weapon and armor at the Forge.
The Templar Archives does not build any units directly, but it is vital for the various units unlocked and upgrades made available. The Templar Archives' own Plasma Shield can be upgraded at the Forge.
The Templar Archives is powered by a Pylon, but even if this Pylon were destroyed, the Protoss would still be able to produce High Templars and Dark Templars.
The two units unlocked by the Templar Archives are powerful ground units. High Templars are devastatingly powerful spell casters, particularly for its Psi Storm. Dark Templars are extremely useful combat units, both for harassment with their cloaking ability and as a powerful melee unit. Two High Templars and Dark Templar can also be merged into Archons and Dark Archons respectively. These units feature other potent spells and attack abilities.
The Templar Archives is generally constructed in all Protoss match-ups for access to the High Templar. The Psi Storm spell is generally the first upgrade researched, followed by its complementary upgrade, the Khaydarin Amulet Energy limit increase. These upgrades are considered universally applicable. In more specialized applications as part of a specific strategy or race match-up, the Protoss player may research Maelstrom spell and its accompanying Argus Tailsman Energy limit increase. The Mind Control and Hallucination upgrades are also highly specific spells only used on occasion in the late game.
In the PvZ match-up, the Templars Archives is generally built by the mid game. It is instrumental in the popular Fast Expand build orders, where the Protoss player will stall the Zerg forces with Photon Cannons until production of High Templars with Psi Storm. These High Templars will continue to be built throughout the remainder of the game against the relatively weak (low hit points) Zerg units. Occasionally, the Protoss player may elect to build research the Maelstrom ability so Dark Archons can aid in countering concentrated Zerg forces. For example, Maelstrom is particularly effective in freezing a group of highly mobile Mutalisks, which can then be easily attacked by Psi Storm or Archons.
In the PvP and PvT match-ups, the Templar Archives is usually built later than in the PvZ match-up, as the Psi Storm is less effective against the relatively strong (high hit points) Protoss and Terran attack units. As a result, the Templar Archives is typically built in the mid to late game, after the Protoss player accumulates a sizable ground force. On occasion, the Protoss may opt for a surprise Dark Templar attack or rush, prompting the Templar Archives to be built much earlier than usual.