The High Templar are powerful spellcasters and can merge to become Archons.
The High Templar are seasoned, veteran warriors of the Protoss armies that have walked far down the path of Khala. Those who choose to accept the mantle of the High Templar set aside the frenzied rage of the Zealot, and instead use their highly potent Psionic abilities to bolster the warriors of Aiur. The sight of enemy forces being torn apart by a Psionic Storm or wasting their firepower on projected Hallucinations is proof enough of the battlefield superiority that the High Templar can give to the Protoss.
Although High Templar are powerless when it comes to physical attacks, their special abilities -- as well as their potential to sacrifice themselves to form mighty Archons -- make them a threat that cannot be ignored.
Hallucination (SC1)Summon Archon
|| Psionic Storm (SC1) (T) 
|| 112 over 7 seconds
| Energy cost
| Cast time
|| 7 seconds
| Used by || High Templar (SC1)
| Inflicts 112 damage to all units within a certain area over seven seconds
The High Templar's StarCraft 2 model