Ahrim the Blighted is the oldest of the Barrows brothers. He uses low level curse spells as well as his set effect "Blighted aura", which lowers the player's Strength. This spell cannot be blocked in anyway, ever. He uses Fire Wave, so it is advised to use the Protect from Magic prayer or wear armour with high Magic defence like Black d'hide armour or Karil's armour. Be wary though, he is still quite accurate on Black d'hide. He can hit a max of 200 using Fire Wave.
Players may attempt to kill Ahrim without Prayer, but it is only recommended if you have 70+ Ranged and 80+ Magic as well as Black d'hide armour. Generally, Ahrim is considered the weakest because he wears robes, as opposed to his younger brothers, therefore making it easier for players to land blows on him. He is weak against ranged attacks.
The name "Ahrim" is likely derived from Ahriman, an evil spirit from the Zoroastrianism religion.
Even if you use the Protect from Magic prayer, his curse spells can still work, plus his set effect still activates because the attack still counts as a successful hit, so bringing a regular stat restore potion is recommended.