Mutant Tarn is a level 69 boss, located at Hellhounds teleport (found in Monster Teleport). You will need to get 20 killcount of either hellhounds or goblins to enter the portal which leads you to Mutant Tarn's lair.
Despite his low level, Tarn has 1000 HP, and can hit up to 900 if you don't pray magic. He is in a multi combat zone, and it is recommended that you organize a team to defeat him.
If you are going to solo mutant tarn, I suggest you have vesta/statius armour to better ensure that you kill him on the first run.
To enter the portal where Mutant Tarn is, you need to kill 20 monsters in the map in order to proceed to him.
Before you enter, you should make sure you are praying against magic attacks, and make sure you have food or law runes just in case things get messy.
If soloing -
When you enter the portal taking you to Mutant Tarn, make sure you have your 'deflect magic attacks' on. What you are going to want to do first is use dragon dagger (preferably p++) special attack, then use your main weapon (vesta longsword, whip, etc.).
If team fighting -
Do the same thing, and just basically rush mutant tarn. With more than two people Mutant Tarn is nothing but a piece of cake. He might hit a 400 on you once or twice within this fight
The most effective way to kill the Mutant Tarn would be to use melee. When it comes to choosing what to wear, it all depends on how wealthy you are in game. An over-average player could use the following equips :
Instead of a Neitznot helmet, you can use a void melee helmet, a berserker helmet, or a statius' helmet.
An amulet of strength/power or Berserker necklace.
An Ardongue cape (3), Skill cape, Obsidian cape, or Spottier cape.
Armor (Top and Bottom)
Fighter Torso / Dragon legs , Statius' plate/legs , Rune plate / legs, 3rd age melee top / bottom, Primal plate / legs / plateskirt, or Full void *(Including Gloves and Helmet)*
Ice / Gold / White / Abyssal whip, Chaotic / Primal rapier, Primal longsword, Chaotic / Primal maul, Bandos / Armadyl godsword, or a Saradomin sword
( The rapiers, whips, and longswords are most effective )
(If item is not two handed) Spectral/ Arcane / Elysian / Divine / Blessed spirit shield, Rune / Dragon defender, Rune berserker shield, Dragon fire shield, Farseer kiteshield, Eagle eye kiteshield, a 3rd age kiteshield, or a rune kiteshield.
( Dragon / Rune defender for increased attack, any spirit shield for good defence )
Dragon / Rune boots
Barrows / Dragon / Rune gloves.
Your inventory should consist of a lot of food, prayer potions, law runes strength/attack potions, and a spec weapon.
For food I recommend using rocktails or sharks, anything other than this would result in you healing your self too slowly, making you more likely do be defeated at Tarn.
For prayer potions, you should use super restores(4)/(3), you should bring two of them.
The spec weapon is optional, however I do recommend bringing a dragon dagger (p++) since it does take away a lot of damage very quickly, making your task of defeating Tarn much easier.
Strength / Attack potions are also optional, but I do recommend bringing them since you do hit a lot better upon using them. An overload would work 2x better if you can afford it.
The law runes are simply in your inventory just to make sure n
Your inventory should look a little something like this :
ZOGRE BONES (100% chances of getting it)
Amulet of fury
Grimy snaps (3)
Rune arrow (25)
Super restore (3)