The khaydarin monolith deals a massive 100 damage a shot and has a long 13 range, equivalent to a siege tank, but has a long cooldown between attacks. It also occupies a large 3x3 space.
The monolith works well as a complement to the photon cannon; the cannons deal lower damage but fire faster, and are cheaper to build. Thus the monolith can help bring down powerful and/or long-ranged enemy targets better with its higher damage, while the photon cannons take care of more numerous, weaker enemies. In larger numbers, the khaydarin monoliths can bring down hybrid units very quickly.
When using khaydarin monoliths, shield batteries are highly advised, as the monoliths have a long warp-in time and are quite expensive.
Karax is able to build khaydarin monoliths in Co-op Missions. Additional upgrades for them are unlocked when Karax reaches Level 6. Karax is instantly able to warp in khaydarin monoliths upon reaching Level 11. Zeratul gains a variant named the tesseract monolith.
Note: The Khaydarin Monolith is not available when using Prestige 2: "Templar Apparent"