Cthulhu Hastur MTL RTA | Review

An impressive MTL RTA by Cthulhu Mod with a few quirks and versatile airflow options.

7 min read

Cthulhu Hastur MTL RTA

Cthulhu Mod is looking to take the crown in the MTL rebuildable market with the Hastur RTA, which offers great flavor and a diverse array of airflow options.


  • Dense saturated flavor
  • Incredibly versatile airflow options
  • Bayonet-style top cap design
  • 3.5ml Capacity
Cthulhu Hastur MTL RTA

I feel like it’s already Christmas! I’ve been complaining to the rest of the team for ages that there are just not enough good MTL RTA’s on the market, and now I’ve been inundated with them!

The Hastur MTL RTA is a 24mm, 3.5ml capacity rebuildable atomizer designed by Brian N. and manufactured by Cthulhu Mod, and is in direct competition with the Digiflavor Siren 2, and Vandy Vape Berserker.

It features a single-coil two post deck, a unique Bayonet-styled top cap design, a clear and frosted glass tank, and 5 swappable airflow restrictors. It is available in both black or stainless steel and comes in one of Cthulhu’s unmistakable old-fashioned tweed boxes.

Note: The product was sent to us by Cthulhu Mod for the purpose of this review.

2Specs & Features
Cthulhu Hastur MTL RTA

Kit Contents

  • 1 x Hastur MTL RTA
  • 2 x ultem drip tips (dia. 2.0mm, 3.5mm)
  • Spare o-rings
  • 2 x post screws
  • Allen key tool
  • 5 x swappable airflow restrictors (dia. 1.0mm, 1.6mm, 2.0mm, 2.5mm, 3.5mm)
  • 1 x frosted glass tank
3Design & Build Quality
Cthulhu Hastur MTL RTA

The Hastur MTL RTA is clean, pleasant and understated in its design. It has a certain Kayfun vibe about it, everything looks and feels minimalistic, refined and elegant. Which is a nice change when there are so many gaudy atomizers coming out of China.

It’s the small attention to detail that gives this tank its character. From the laser-etched logo on the chamber, the wavy line engravings decorating the top cap and base, to the darker hue of Ultem used for the drip tip. They all add nice touches to the overall aesthetics of what is a well-designed, good looking tank.

It is also well-machined, all the threads are nice and smooth which is what we’ve come to expect from Cthulhu. However, it’s not entirely void of its design flaws….more on this later.

4The Deck
Cthulhu Hastur MTL RTA

Cthulhu Mod is touting the chamber as “Probably the smallest chimney chamber RTA.” I’m not sure why you’d choose to use the word “probably” in your advertising, but I can tell you it is a small chamber.

This is mainly down to the positive and negative blocks in the build deck using up most of the space, but this is for a good reason. What’s that you reason you say? Well, firstly, it’s believed that a smaller chamber leads to an increase in flavor, I’m not sure if that’s true or not, but it is becoming a common trend in flavor atomizers.

Secondly, it means the Hastur has room for a two post design with two slotted terminals, just like that of the Serpent SMM. I love this style of build deck because it means there’s no need to think about which way your coil legs are facing, just chuck your coil in any way you want to….nice and easy.

Surprisingly, even with such a small chamber, the deck can still manage to accommodate 3mm coils with ease. The post screws are not the smoothest I’ve come across, and I’m not really a fan of flathead screws, but it does get the job done and traps your wire securely in place.

The one glaring problem I have with the design of this tank is that there is no way to remove the build deck when it has liquid inside – unless you want a flood of juice to spill out everywhere. This is due to the glass section only being held in place when you screw the top cap and base section together; there is no super chunky o-ring or groove to keep it from shifting. This might be fine for some, as they may only require access to the build deck when the tank is empty. However, it really frustrated me as I like to change wicks regularly, and sometimes mid-tank. I nonchalantly forgot about this limitation on one occasion and was left with a table soaked in juice and the harrowing cries of why Cthulhu?…..why?

Cthulhu Hastur MTL RTA

A lot of MTL atomizers suffer from gurgling and leaking after they have been refilled. This is usually caused by the pressure exerted into the chamber when you screw down the top cap down.

Cthulhu has opted for a bayonet-style top cap to try to remedy this. To refill, you grab on to the nut affixed right above the top cap, push down and turn it clockwise or anti-clockwise. You will feel the top cap detach from the chimney when it lines up properly.

To replace, simply line up the protruding ends with the indentations on the chimney and turn it clockwise or anti-clockwise to latch it on.

It is similar in design to that of the Siren V2. However, I feel it isn’t quite as easy to remove and does require a bit more force to push down when you are trying to lock it. That may also just be an issue with our sample. On the whole, it’s a good top fill system, and I could see more manufacturers using this bayonet-style top cap in the future.

Cthulhu Hastur MTL RTA

One thing Cthulhu have got you covered with is airflow options. The Hastur MTL RTA comes with not one, not two, but FIVE different airflow restrictors. If that’s not enough for you, then there is also an option to purchase the ‘airflow resister plus’ for even more choice.

I tend to prefer a more open mouth-to-lung vape, and I really enjoyed using the 1.6mm and 2.0mm restrictors with the bottom airflow wide open. I think this is, in my opinion, where the Hastur beats the Siren and Berserker by providing more versatile options in airflow. If you are a fussy vaper like me, you can really dial in on the perfect MTL setup. Although it’s not as straightforward as using the Siren’s bottom airflow adjustment, as you have to install the restrictors (and even more of a pain when the glass doesn’t stay in place!)

The Hastur not only allows you to go right down to an incredibly tight draw, but you can also remove the restrictor altogether (or use the 3.5mm) and have a rather impressive restrictive lung vape, not something I was able to achieve with its competitors.

In whichever configuration I had the airflow setup, the flavor and performance were excellent. It’s now got to a point with these MTL RTA’s that I’m hard pushed to say which one is the best for flavor. I own both the Berserker and the Siren V2, and the Cthulhu Hastur definitely holds its own in the flavor department.


  • Highly customizable airflow
  • Dense saturated flavor
  • Good machining
  • Easy to install coils
  • No leaking
  • Bayonet-style top cap design


  • You can’t remove the build deck when tank is full
  • No 22mm option for smaller mods

Cthulhu Mod has not reinvented the wheel here. What they have done is borrow, tweak and refine ideas from other great atomizers and making something worthy of being my go-to MTL RTA.

In the last few weeks of testing the Cthulhu Hastur, I have not gone anywhere near my other MTL tanks, and believe me, that’s not always the case when reviewing products. This has mainly been down to the fact I could fine-tune the airflow to my exact my preference.

However, this tank is not perfect. One of the few minor, or major quirks depending on which way you look at it, is the fact you cannot remove your build deck when the tank contains liquid. I’m not sure if this was an oversight on their part, but I just wish Cthulhu included better o-rings or took note that some of us like to remove the deck and keep our liquid in the tank.

That being said, they have designed an impressive MTL tank, which produces amazing flavor and is worthy of joining the ranks of the Siren 2 and Berserker RTA in the upper echelons of the MTL category. In fact, if it were on looks and airflow options alone, the Hastur MTL might be my top choice.

Check out Vaping V1ck’s YouTube channel and his video review of the Cthulhu Hastur MTL RTA below.


Build Quality
Build Deck

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Cthulhu Hastur MTL RTA | ReviewCthulhu Mod is looking to take the crown in the MTL rebuildable market with the Hastur RTA, which offers great flavor and a diverse array of airflow options. Dense saturated flavor Incredibly versatile airflow options Bayonet-style top cap design 3.5ml Capacity 1Intro I feel like it's...