The Knight-Incantors are gifted stormcallers who can summon hurricane winds and gales of mystical energy against those who cannot be slain by conventional weapons. They are second only to the Lord-Arcanum in rank in the Sacrosanct Chambers and often lead brotherhoods in the absence of the chamber’s commander. 
When attending the Anvil of the Apotheosis, the Knight-Incantor sings the music of the spheres in celestial melodies to calm and reorient the souls that undergo reforging. In battle the Knight-Incantor uses the same voice to draw in motes of magic, marshalling celestial power into howling gales, lightning shocks or to summon a downpour of freezing hail. Their magical songs can draw spiritual energy toward them, which they capture in a spirit flask carried at the waist.
All Knight-Incantors are equipped with an "Incantor’s Staff" which is also their rods of office which can channel the energy of the storm into a raging hurricane, or crackling bolts of arcane power. Many carry scrolls imbued with potent void magic which are able to dispel the hostile emanations or baleful spells unleashed against them by their enemies.
In times of great need the Knight-Incantor can hurl one of the spirit flasks into the midst of the foe, which then shatters with a thunderous explosion that sets loose a frenzied storm-spirit that ravages all those who stand near with wild celestial energies.
- 1: Battletome: Stormcast Eternals (2018) - Knights of the Stormhost - pg.68
- 2: Knight-Incantor Warscroll