A random encounter is a scavenger looting some dead soldiers. At level 27 I sniped him with a poisoned elven arrow with no effect (77 archery)
He knocks Argis in one blow, dispatch the dremora summoined with the sanguine rose and kills my character in one hit. Meaning he bypasses all armor and lends more than 400 damage
Is there a tutorial about how to kill him or the point is just to run as fas as possible when we spot him ?

Be thankful you don't play dead is dead.