magical Attacks have Disadvantage against them

Saving rolls against Spells from them have Advantage

They get only half of the healing of a Healing Spell (like Cure Wounds or Heal) to the Hitpoints
Healing Potions works normally fine with them

If they get hit by a Magic attack the Player must roll a Percentage Dice and reduce the Damage by the rolled percent

(Example a Firebolt with 10 Damage would hit them the player rolled a 80% on the Dice the damage would be reduce by 80% from 10 damage to 2 Damage)

Advantage at Death saving throws

After Level 10 they are Immune against Fear effects

once they fall unconscious in a fight they can get up with 1 HP it's resets after a Short or Long Rest

after they where unconscious in a fight they get at
Level 1 1D4 Bonus Damage
Level 6 1D6 Bonus Damage
Level 12 1D8 Bonus Damage
Level 18 1D10 Bonus Damage
Level 20 1D12 Bonus Damage
the Bonus Damage resets after a Short or Long Rest

+2 to Strength or Dexterity

+1 to Constitution

At Level 15 the Player can for one fight raise the Damage output by 1D12 and it resets after the fight and can't be used until the next Long Rest

At Level 20 the Player get the Bonus 1D12 for Two Fights and resets with the next Long Rest

After use the Ashra suffer 1 Point of Exhaustion

At level 1, 5, 10, 15 and 20 the Player get a additional Hit Dice

In a Fight the Player can Use up to 5 Hit Dice to get HP back

Language, Commonsense etc.

As a Magic Resistend being is the Ashra a quite capable and deadly enemy of all kind of Magic Users.

Most of the Ashra a teached in the Way of Mage Hunters, because of the Magical Resistance they are often hired to hunt down rouge Magic Users