SCINTILLATING LEGIONS units from your army have the following the ability:
Daemonic Illusions (Aura): While a friendly THOUSAND SONS PSYKER unit is within 6" of and visible to this unit, models in that unit have a 4+ invulnerable save against ranged attacks.
THOUSAND SONS units from your army have the following ability:
Mortal Sorcery (Aura): While a friendly SCINTILLATING LEGIONS PSYKER unit is within 6" of and visible to this unit, that SCINTILLATING LEGIONS unit has the Cabal of Sorcerers ability.