Chaos familiar

Use this Stratagem at the start of your Psychic
phase. Select a THOUSAND SONS PSYKER
from your army. That model can replace a single
psychic power with a power of your choice from
the Dark Hereticus discipline, Discipline of
Change or Discipline of Tzeentch.
Though diminutive in stature, many lesser warp
entities whisper dark secrets that can shift the tide of
battle.