Zulrah is known for its regular good drops and high gold-per-hour rates as well as the comfort of being a solo-only encounter. It will require to make a lot of preparations but don't let this discourage you from trying, it's an effort worth making. It's invulnerable to melee attacks and, therefore, instead of a high Melee skill you will need the following: 80 or higher Ranged skill level, at least 70 Defence skill level with a score of 80 in Magic and Hitpoints skills and 45 or higher prayer skill.
You can get yourself Magic and Ranged armour and weapon sets (ie Armadyl armour Mystic robes, toxic blowpipe and Trident , the swamp) Casting runes, food (we would recommend shark and monkfish) or combo food for gaming purposes, anti-venom, ranging, prayer and magical potions (for the last one alternatively imbued with heart) rings of recoils or some other form of teleportation like Home Tablet the last and certainly not the least, Runes for"Vengeance" spell.
To unlock the fight you'll have to get to Port Tyras in Regicide questline. After that, you'll need to make yourself as an offering to the High Priestess Zul Harcinqa, after that you're all set to try your luck against the serpent god.
Last boss in the Dragon Slayer II quest chain with proper equipment, stats and bit of skill can be taken down thirty times per hour . This can yield staggering quantities of gold in an hour.
The collection of the right equipment isn't simple, but with enough effort , it's totally doable The following is what you'll need it. At least 90th-level of Hitpoints, and the ability to range, 80 in defence and 74 in Prayer. Dragon crossbow hunter (it's the best possible weapon in this fight and allows you to increase the kill count to even at 34 per hour, as your skills develop! ) Dragonfire ward Ruby dragon bolts and equipment for void knights (elite one) Ava's accumulator, its cool bonuses for ranged attacks, Salve amulet as Vorkath is undead. Pegasian boots, archers ring , and of course potions and food. It is a good idea to bring some type of teleportation gadget (for quick banking) along with a Rune pouch. Good luck!