Welcome to my Zamorak Guide!
While fighting this boss you'll be praying magic so you need to stack range and melee defense. Melee barrows will do just fine and I highly suggest Guthans. You can heal off the magic and melee minion once K'ril and the range minion are dead and you'll use little to no food per kill.
My Set Up
K'ril and his minions drop food and potions often. They drop Tuna Potatoes, Sharks, super restores, and super attack/strength potions. So I bring 3 and sometimes more Sara Brews, some food to start off and the super combat and a few super restores to hold me over until I get the potion drops. If you get lucky with supply drops you could honesty stay here forever!
This is just my set up and I'm a poor noob so change it around as you like! I suggest a DFS if you have one and a better spec wep. Although, with this set up I have no problems killing this boss.
Let's start with how to get there, that might help a little. Use the Boss Teleport and click on Godwars Dungeon. Once you arrive run a little North east and follow my map!
To be able to get into the boss room you must first either get 25 Zamorak Kill count or a Ecumenical key. Ecumenical keys allow you to enter the room so you don't have to get KC. If you're nervous about killing this boss I suggest having a spare key in the bank so you can re-enter the room right away to get your stuff! Ecumenical keys are rare drops that any monster in GWD drops. If you're lucky you could get one while you're getting KC to skip this mini grind.
This is the best place I find to get KC. You can semi afk and the bloodveld and the werewolf will always agro you so you can just sit back and let your characeter kill them. Be sure to watch if they drop a Ecumenical key thought!
TIME TO START KILLING
Once you have either 25 KC or a Ecumenical key run a little south and get ready to start killing! Once you get by the door brew and pot up and pray magic.
Right when you enter the room and run north of the boss a little to block the melee minion (Level 145) behind K'ril so you don't have to tank his damage while you kill the boss. Than just pray magic and go ham!
After you kill K'ril run a bit east and get the melee minion in between you and the range minion (Level 142) and kill the range minion!
Once you kill the range minion you should not take anymore damage! Run north and hide behind the mage minion (Level 151) and kill him. This is a great time to use guthans if you have it because you'll be taking no damage.
After you kill the magic minion pray melee, continue to use guthans if you're not full hp, and kill the melee minion. Stay at the north end of the room though by the altar. Every once in awhile you can use the altar to get full prayer for free but you can't pray while you're in combat so once you kill the melee minion spam on the altar!
Than final once the melee minion is dead, you have full hp and pray, run a little south in between all the loot and repeat! Be sure to put magic pray on right after you kill the melee minion because they re spawn fairly quickly and you don't have to get 1 banged by K'ril!
Use Piety as you like, keep in mind the massive prayer drain though. I normally use it while I'm specing K'ril or when I have a large amount of super restore potions.
This is the best part! All the spoils you'll be taking away :D. One great thing about camping here is even if you don't get a big drop you will still make a decent amount of money because K'ril and all 3 of his minions drop coins and they add up extremely quickly!
Some big drops are:
Zamorakian Spear (You can talk to Otto Godblessed at home and he'll make it into a Zammy Hasta for you for 3m GP, the Hasta is a great weapon to kill dragons with!)
Zamorak hilt (Use a Godsword Blade on this hilt to make a Zamorak Godsword)
Godsword shard 1,2, and 3 (If you get all 3 of these shards you can make it into a Godsword Blade and use it on any Godsword hilt to make a full godsword!)
Staff of the dead
Rune sword (Troll drop, if you get this drop know you could've gotten any drops above this one. Sad Times.)
Pet K'ril (An extremely rare drop where you get a sweet mini version of K'ril to follow you around where ever you go!)
K'ril has the best chance of dropping any of these drops but the minions also have a extremely rare change of dropping these items! (Besides the pet)
Thank you so much for reading my guide, I hope it helped! If I missed anything or you have any questions please let me know! Also if you want to suggest what guide I should make next that'll help me out!