Go upstairs and earn an elemental spear with 2 clad mind bars. Go back to
RuneScape gold the body space, wield your new spear, and pull on the lever in the center. You may wield only mind armor against the Homunculus. After the fight is finished, your brain armor will probably have turned to Elemental Balance Armor. This armor has gentle melee stats. The spear (or, even if you've progressed sufficient through barbarian training, hasta) has medium melee stats, and will auto cast spells as well.
Go Back to the Ancient Cavern and try to go through this Mithril Door. You may succeed. There'll be several Nightmare Terrors and Nightmare Spikes (Nightmare Spike-level 62, ranged user, can switch off your prayer randomly) attacking you. At the center, the critters will vanish, and a phantasm appears. The Phantasm is revealed to be part of Zaros's soul. He'll attack you, inflicting massive harm if you don't have at least one piece of rotten equilibrium armor, or even the weapon.
He utilizes Ancient Magics, such as Miasmic, as well as ranged along with a melee attack with a power dip. Defeating him is much more of a battle of wits than most battles you fight. He appears in the center of
buy RS gold the point, does an emote, disappears, launches an attack (at the ground, not in you, so you are able to dodge), disappears, repeat and rinse. I will not go into specifics about what happens, come up with it yourself. If you understand what attack is coming, but not where it will be you can use astrology, however everytime you use prayer to block an attack, then your prayer is drained several points.