Although gorillas require an enormous amount of effort to defeat at first, they are one of the top PVM cash-making options in OSRS, so overall it is completely worth the effort. Before we go to the actual guide on how to defeat them, let's look at the items you need to bring to battle evil gorillas.
Quest/Stats Requirements
It's important to remember that one of the requirements is that you have completed Monkey Madness 2 to unlock Demonic Gorillas.
In addition, you'll require at least 80+ combat-related skills. Magic Spells and Protection Prayers will be needed (70+ prayers recommended).

Gear Setup
Here are some fundamentals about gear.

Example Setup
Best in Slot
* Slayer Helm. The Serpentine Helm, Void Melee, Void Melee, and Ranged are all great options in the event that you don't have one.

* Infernal Cap. You can also use a Fire Cape or Ardy Cloak.

* Ava's Assembler. This can be useful for activities that require a lot of variety.

* The Amulet of Torture/Necklace anguish. They will permit you to create serious damage. Bring an Amulet of Fiery to switch between.

* Rada's Blessing 4. Attained after you have completed all the most difficult Kourend & Kebos diary tasks You can wear this for a bonus prayer.

Weapons will depend on the capabilities of the weapon, but there are a few options that can be used to fill those slots.

* Arclight. It is the most effective melee weapon for any demon and is quite easy to get. The Ghrazi Rapier is the next best choice and is followed by an Abyssal Tactacle.

* Twisted Bow and Blowpipe. Karil's Crossbow is an excellent choice as well.

* Avernic Defender. This might not be needed in the least however it's a good idea to bring a ranged shield such as the Avernic Defender or, in all cases it's the Dragon Defender.

* Barrows Gloves. These gloves are top of the line for range and second-best for Melee. It is not needed, but you can bring Ferocious gloves to switch.

* Primordial Boots. The most effective melee boots in the game followed by Dragon Boots, which are an affordable alternative to.

* Berserker Ring. This is the ideal ring option to fill the hole in your ring. You can also infuse it with stats to increase the number of stats. A Brimstone Ring, or a Ring of Suffering could be utilized.

Inventory
Within your Ranged Switches, it is an ideal idea to have between 3 to four of them.

Your weapon is your top priority, since it's the only method you have to do range damage.
Also, you will need to make sure you have an Ava as well as boots and an amulet switch in the event that it is possible.
Killing Demonic Gorillas
There isn't a simple way to eliminate Demonic Gorillas. It is necessary to be consistent and master the process of changing gears and praying. Although it's not that difficult, perseverance is crucial.

Their attacks are not always apparent to you. They are able to target you using any combination of these three kinds of attacks.

It's a range attack that looks almost like someone is taking a chunk of white rock and throwing it towards you. This is why you should to be praying for to be able to range.
They typically swipe their claws using their teeth in the melee. This is where you pray for to use melee
A magical attack that manifests in the form of a green blob. In this case, you can pray to the to a wizard:
It also can be used to perform an attack in combination with an axe toss or a magic. Make sure to pray for magic:
Gorillas will employ a defense prayer to shield you from harm when they approach. Keep that in mind when you plan your attack. After you've accomplished enough damage, you're going to switch the overhead prayer to whatever you are battling with.

Typically, for each 50-damage point that the switch occurs, the first time a gorilla switches over is usually just a bit earlier. That means that you'll have to replace your gear after 50 damage.

Gorillas aren't likely to switch to a different attack technique if they're not doing any harm. That means that when they hit 3 zeros with any kind of attack it is likely that they will switch their attacks.

Demonic Gorilla Location
You can utilize a royal seed pod to reach the area where the demonic gorillas live (the one that you obtained after completing Monkey Madness 2) in order to reach the gorillas. It can be found just north of Tree Gnome Stronghold. It is visited in the final battle against monkey madness II.

Once you've entered the caverns , you'll be required to turn off range or protect from mage, and then go through the passageway into the combat zone. You can fight multiple gorillas at a time or take them on as a team. There is a good chance that you will be attacked by a gorilla prior to you even decide which one to fight. Pray to stop any attack from them.

You should not do too much damage. After you have smashed the attack, you should determine what the gorilla is praying to help choose which weapon to use. If the gorilla uses prayers from afar then you could employ melee. If it is praying to shield itself from melee and is praying to protect itself from melee, you can employ range.

Once you've got understanding of the gorilla's attack and the gorilla's prayerswork, it's going to become easy from that point on, but be aware that each time they change their overheads it is necessary to switch your weapon and, ideally, the offensive prayer.

Tips and Tricks
If you walk away and the gorilla follows your steps and follows your steps, it'll change into melee.
You can take some damage when you have to make a guess.
If you see a rock falling from the ceiling, walk away from the area immediately.
You can utilize the royal seed pod to access the Grand Tree or bank once you have run out of food and prayer potions.