Mutant Tarn is costume boss for Tibikra. Its for medium - high level players designed boss. He is fairly easy boss and with medium gear you can get 5 solo kills per trip.
He is weak against ranged attacks (crossbow) and you can reduce his damage with Dragonfire shield (-20%) or DragonKite shield(-50%)
If you don't have dfs you can try to wear anything with range bonus. Also you can use void set instead karil's.
You can use Dragon bolts(e) instead onyx but with onyx you can stay longer.
You can get Dragon token from Mutant tarn. You need to combine Dragon token with your Dragonfire shield in order to get Dragonkite shield.