Arcane Genetic Alchemy

Use this Stratagem in any phase, when an
ADEPTUS CUSTODES unit from your army (excluding VEHICLE units) is selected as the
target of an attack. Until the end of the phase,
each time an attack is made against that unit, an unmodified wound roll of 1-3 for that attack fails, irrespective of any abilities that the weapon or the
enemy model making the attack may have. if that ADEPTUS CUSTODES unit contains 3 or fewer models, this stratagem costs 1CP: otherwise,
it costs 2CP.