Sub-Ohm Tank Reviews

Cthulhu RTA

Cthulhu pronounced "Cu-thule-hoo" or "Cu-tool-oo" is a particularly loathsome creature created by horror writer H.P. Lovecraft. On the other hand it is also a massive airflow dual coil RTA it is made by Cthulhu Mod a new manufacturer from Shenzhen, China. It has been nicknamed by many as the "Goblin Killer".

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Introduction to the Cthulhu RTA

Cthulhu, so I'm sure you're asking how do you pronounce that, what on earth does it mean?

Cthulhu pronounced "Cu-thule-hoo" or "Cu-tool-oo" is a particularly loathsome creature created by horror writer H.P. Lovecraft. This being is utterly alien to us and possesses terrible powers. His race is commonly referred to as The Great Old Ones  Banished by another powerful otherworldly race to his city R'lyeh beneath the Pacific Ocean Great Cthulhu sleeps but has the power to influence people in dreams, also through bizarre ancient artifacts, writings, rituals and incantations etc. He has many human worshippers who would like nothing better than to release him from his prison. Typically these misguided fools dabble with the occult and carry out their alien master's rituals in a bid for personal power but typically their efforts go awry resulting in insanity or death. Should Cthulhu ever awake and rise again he will devour the world. Lovely grim stuff isn't it?

The Cthulhu RTA on the other hand is a massive airflow dual coil RTA  (Rebuildable Tank Atomizer) it is made by Cthulhu Mod a new manufacturer from Shenzhen, China. While it shares many apparent similarities with the Youde Goblin RTA it is a completely authentic design and not a clone. For all intents and purposes it has been nicknamed by many as the "Goblin Killer".


  •  Medical grade stainless steel
  • 4ml capacity tank
  • Massive 3mm airflow w/AFC ring
  • Top refill & bottom refill design
  • 4x  2.5mm rounded juice channels
  • Negative posts are milled into the deck
  • Dual coils support (Diameter 1.6mm wire hole)
  • Two independent air flow channels (Air flow does not touch copper 510 pin, meaning better flavour)
  • Cross section of chimney is larger than the sum of two air holes
  • Pyrex Clear tube
  • Height: 55.5mm / 2.18 in (without drip tip); 70mm / 2.75 in (with drip tip)
  • Diameter: 22mm / 0.87 in
  • Capable of 50w plus with ease.
  • 510 pin is non-adjustable

What's in the box?

  • Cthulhu RTA with drip tip
  • Allen key
  • Spare Hex screws.
  • Spare O-rings
  • Two pre-made coils
  • Authenticity card

Cthulu Styling

It's actually a rather nice looking tank especially with the Cthulhu octopus/squid like face laser etched on to the chimney section. For Lovecraft fans Cthulhu watches you while you vape sensing your weakness.

The tank also had the faint aroma of machine oil so everything was fully cleaned before use. I thought the packaging was done well with the Cthulhu logo stamped on a transparent press lockable box. The spares on the whole are good value and the authenticity card provides a code you can check on Cthulhu Mod's website.

Cthulhu RTA Build

While I haven't built lots of tanks in my time as a vaper I have certainly done a few and I've had minor issues with some of them but I've always managed to get a satisfactory build completed and end up with a decent vape. The Cthulhu RTA in my honest opinion is one of the most frustrating and annoying tanks I've built. I've read accounts of people saying this is an easy build, all I can say to that is the one I received for review was an exercise in pain and suffering.

The major problem is what I refer to as Cthulhu's Key of Uselessness. The supplied Allen key is the flimsiest and possibly worst made that I have ever come across. Such is it's desire to bend and twist out of shape at the slightest amount of pressure that you'll end up thinking its constructed of rubber or being purposefully warped by malicious sorcery.

The next issue is the hex screws which I took out my frustration in calling the Hexed Screws of Torment. They don't trap the wire well or hold it firmly in place. After tightening them over and over again with the ever distorting Allen key they still have a habit of not gripping the wire and letting it slip out the post holes at a moments notice and what at first glance appears to be a secure coil actually is only secure for a while until it decides to once more come loose again.

Through sheer perseverance and the desire to bring you all a review I kept at it. I firstly tried with 0.4mm (26 AWG) then with the two supplied coils which to be frank were less than ideal. Then on my third attempt I tried 0.5mm (24 AWG).

Each time I was thwarted by the terrible screws which refused to tighten sufficiently. My final attempt I went back to 0.4mm wrapped around a 2mm screwdriver and on this one occasion and after applying quite a strong amount of force to the screws it did eventually trap properly.

My final build was a dual coil, 0.4mm (26 AWG) Kanthal at 0.4 ohms resistance.

Wicking was actually quite straightforward after all the preceding madness. I used Japanese cotton and primed the wicks with South Coast Vape's CYMore and positioned them in the top of the juice channels being careful not to block the channels themselves. In the case of the Cthulhu less is actually more and it pays dividends to keep the wicking as short as possible. Things started to get much simpler as I screwed on the chimney, fitted the glass and then added the top fill cap.

Clearly things were going too well because then I discovered the next issue with this RTA. The nut that screws the chimney section to the top fill cap is a really tight fit. The threading isn't particularly well done and upon inspecting it from underneath it appears somewhat warped. It took quite a bit of effort to get it to tighten down. When I had got it in place I tightened it up with a pair of pliers.

I had already read in various accounts that it is wise to close the air holes when filling this tank so I proceeded to do that, queue yet another problem. The airflow control is seriously stiff and you really need to apply quite a bit of force. In fact it only seems to turn when you remove the RTA from your mod. I suspect the O-ring inside it is too thick and that this is the cause of the issue so if you have similar problems it may be worth looking at replacing it.

Once filled up with CYMore I then screwed on the top cap cover/drip tip adapter. This was also of questionable threading but nowhere near as bad as other parts of the RTA. Although the drip tip itself was somewhat wobbly and could use an extra O-ring or some dental floss wrapped around it for a better fit.

Vaping the Cthulhu

Well that's the best thing about it. The vape is actually fantastic, at least for me. I have long desired to find a tank that has a huge amount of airflow and has flavour on par with a RDA. This tank in my opinion achieves that. I set the airflow slots fully wide open and it was the perfect setting for me.

CYMore had far more depth to it than I typically notice on a dripper, the flavours blended superbly and complemented each other. I found it even picked up subtle flavour undertones that to be honest I never realised were there.

I vaped at various wattages from 32 watts to 85 watts on my Sigelei 100w+ and I found the vape warm with excellent clouds produced which were very dense. The flavour was gorgeous so I continued to vape away and before I knew it the tank was almost empty. This RTA drinks your juice extremely fast and if you are on a budget then stay well clear.

I cleaned out the tank and then tried it with some DIY peaches and cream and once more the vapour, flavour and airflow were perfect for my tastes. The wicking kept up constantly despite me heavily increasing the wattage.

At no point did I actually have any leaks but I did find myself refilling the tank often such was my need to vape on it once more. Its highly impressive in the actual performance department and I enjoyed it greatly.

In comparison to a RTA such as Kangertech's Subtank Mini this completely blows it out of the water in the airflow, vapour and flavour department. In fact it literally drags the Subtank down beneath the waves with powerful tentacles to suffer in awe at the power of Great Cthulhu. OK so I embellished a little there to keep to the overall theme but the tank excels where it needs to.

I will not even speculate on whether this tank is better than a Goblin since I have never used one and it would be an unfair comparison without first hand knowledge.

Does the vape quality make up for all the other issues?

That will depend a lot on your own patience and build skill. It will also depend on how well machined the RTA you receive is. For me its a yes and no answer. I love vaping on this RTA but I am mindful of how frustrating it was for me to build.

The screws are the biggest issue and I also feel the post holes are oversized and this is causing the majority of my frustration. The weak threading I can excuse to some degree but not the essentials. The hex screws are 0.9mm so its easy enough to get a proper Allen key in that size. I also found some spare Philips screws from of my RDA's that did actually fit the only issue was the double centre post and the fact the screw head overhang prevented them both from fitting. There will be some solution to this out there and I will continue to look for it.

Is it just me or are there some real concerns here?

Like I said I have built a few tanks before, even though I am now a heavy RDA user I do know how to put a build in a tank.

I looked around online to see if others were experiencing any similar problems. A few  had some concerns, others commented on slightly iffy machining and others had no real issues at all. So a bit of a mixed bag and it does suggests some QA or production line errors.

I decided to email Cthulhu Mod directly and get some clear answers. I was very quickly responded to by Joshua from Cthulhu Mod in China who was very helpful, extremely mindful of the issues raised and was very interested in any feedback that would help them iron out these technical difficulties.

The following is my questions to Joshua and his responses.

My RTA has very stiff airflow control adjustment. Possibly due to the O-ring being larger than necessary.

We changed the O ring in next batch.

The nut that screws down to hold the top filling cap and glass in place has very bad threading on the post and requires some degree of force to tighten.

We will remove the nut in V2, and we will make thread on the top cap.

Every wire type used continually works itself loose. The hex screws do not seem to press down securely enough and with the model I received they appear slightly too short.

V2 will use Phillips screws.

The top cap/510 adapter piece has some warping/distortion underneath. Also it requires some pressure to screw on suggesting less than ideal threading.

I will talk this issue with technician and he will find a way to fix it.

The post holes on the model I received seem to be drilled too large and leave too much space for wire to come loose from the hex screws. I have tried 0.5mm Kanthal (24 AWG), 0.4mm Kanthal (26 AWG) and double twisted 0.4mm (26 AWG).

We will use Dia 1mm wire hole in the V2 version.

So as we can clearly see there are a few issues, the manufacturer is aware of them and

is very keen to fix all this in the Cthulhu Version 2. When that will be available I cannot speculate but Cthulhu Mod did promise to send a Version 2 RTA to Planet of the Vapes for review when it is.


A absolutely fantastic vape. In the same league for flavour as a good RDA but better in some respects due to the way it blends in the tank. Amazing vapour produced but at a cost since its a very heavy juice guzzler.

Sadly the build quality is somewhat off in places but the manufacturer is keen to remedy the problems and listen to all feedback. I found them to be very friendly and approachable and they showed a real drive to keep pushing to improve their product.

If you are desperate to try this tank and can live with its problems then feel free to purchase it. After all it is entirely possible that the tank I received for review had more issues than others.

However if you are the slightest bit concerned I would hold off for the moment and wait for the arrival of Version 2.

Remember this was just the first encounter and Cthulhu shall rise again.

Dave Junglist avatar

Dave Junglist

Reviewer at POTV
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Dave Junglist is co-owner of Planet of the Vapes and has been vaping since 2015.  He spent his early years with his head in a bass bin and was a very committed and experienced smoker.  He had his first cigarette at the age of 13 and just knew it was for him.  He did stop briefly with the aid of patches but reverted quickly and became a ‘secret’ smoker, working hard to keep his weak will from the attention of his family.  Vaping made an honest man of him and for this he is forever thankful. He has been involved in websites since completing a degree in Environmental Science in the late nineties.  At that time there was pretty much no contact with computers but on joining the regular workforce and deciding that the world-wide-web was the future he blagged his first job as a web designer and never looked back. As you would expect from a junglist, Dave likes his beats and is most comfortable when the bass is wobbly.

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