It is highly recommended to use the Protect from Melee prayer before speaking to him and and accepting his challenge, as he can hit up to 57. Although Kob can hit through Protect from Melee, he will deal far less damage if it is active.
Players can safespot Kob by running out to the door, as he will not be able to reach you. However, note that using a halberd will NOT prevent him from reaching/attacking you. When he is defeated, Kob will beg for mercy and agree to not help the monkeys.