Luck is a powerful trait that gives units a 75% chance to evade any damage from external sources that would otherwise kill them.
Luck is given by:
The Luck spell
, which requires 1
and Alteration 3,
The Personal Luck
spell, which requires 1
and only Alteration 1 but only affects the caster,
Several Magic Items
, which only your Commanders can use,
And the Luck Blessing
, which requires 9
Bless points and 2 Fortune on your Dominion scales
, and which effects all of your Blessed units while your Pretender
is awake and alive.
Luck is amazing to have on chaff (small frontline troops who you don't count on living) and is a decent layer of protection for your weaker Commanders against ranged attacks. You shouldn't press your Luck too hard, though.