12 Bolts of Thunder Slot Review (Thunderkick)

RTP: 96.15%

Provider: Thunderkick

Best casinos: All British Casino, Fun Casino, Dream Vegas, Grand Ivy Casino, Las Vegas Casino

12 Bolts of Thunder Key Features

RTP: 96.15%

Provider: Thunderkick

Volatility: High


Reel style: 5x4

Paylines: 20

Stakes: £0.10- £100

Max Win: 30,000

Free Spins


prize table


Casinos that offer 12 Bolts of Thunder slot sorted by RTP

100% up to £300 + 25 bonus spins on Starburst

  • Wagering req. 35x
  • Value/free spin £0.10
  • Offer amount £302.50
18+. New players only. One bonus offer per player. Minimum deposit £20. Max bonus bet is £5. Bonus spins on selected games only and must be used within 72 hours. Bonus funds must be used within 30 days otherwise any unused bonus shall be removed. Bonus funds are 100% match up to £300 on your 1st deposit. Bonus funds are separate to Cash funds, and are subject to 35x wagering the total bonus & cash. Only bonus funds contribute towards any wagering requirements. Terms apply. GambleAware.org.
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100% bonus up to £123

  • Wagering req. 50x
  • Value/free spin £0.10
  • Offer amount £123
Welcome bonus for a new players only | Maximum bonus is 100% up to $/€/£ 123 | Min deposit is $/€/£ 10 | No max cash out | Wagering is 50x bonus | Maximum bet while playing with a bonus is $/€/£ 5 | Eligibility is restricted for a suspected abuse | Skrill and Neteller deposits excluded |
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100% up to £100 + Always 10% Cashback!

  • Wagering req. 35x
  • Value/free spin -
  • Offer amount £100
#AD New customers only, min deposit £20, wagering 35x, max bet £5 with bonus funds. Max bonus is 100% up to £100. No max cash out on deposit offers. Welcome bonus excluded for players depositing with Skrill or Neteller. Cashback is cash with no restriction. Full T&C’s apply
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100% Match Bonus up to £300 + 150 Bonus Spins

  • Wagering req. 35x
  • Value/free spin £0.10
  • Offer amount £315
Max bonus bet £5. Offer: 100% bonus match on 1st deposit + bonus spins. Value of bonus & number of spins depend on deposit amount: £20-£100: max £100 bonus + 50 spins on selected games; £101-£200: max £200 bonus + 100 spins on selected games; or £200+: max £300 bonus + 150 spins on eligible NetEnt Games. Winnings from spins credited as bonus and capped at £100. Bonus funds are separate to Cash funds, and are subject to 35x wagering the total bonus & cash. Only bonus funds contribute to wagering requirement. Bonus funds expire within 30 days; bonus spins within 72hrs. Affordability checks apply.
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100% Welcome Bonus up to £200 + 30 Free Spins on Book of Dead

  • Wagering req. 40x
  • Value/free spin £0.10
  • Offer amount £203
New players only. Opt-in Required. Wager from real balance first. 40X wager the bonus and the winnings from free spins. Contribution varies per game. Selected games only. Wager calculated on bonus bets only. Bonus valid 30 Days from receipt/free spins valid for 7 days from issue. Max conversion for free spins: £100. Excluded Skrill and Neteller deposits. Withdrawal requests voids all active pending bonuses
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100 Spins Test

This 100 Spin test was updated by Steve Madgwick on 1/2/2024

In this video, I play and review a brand new slot game from Thunderkick, 12 Bolts of Thunder. I do 100 spins with and count the number of wins, check the RTP, volatility, and hit rate. We also hit the free spins bonus round and analyze the session's profitability. Don't forget to scroll down for the full review and game data and slot sites to play at. Enjoy!

100 spins is not a Real Test

We give every slot a 100 spin test to see just what it can do, or not as the case can often be - 100 spins is no reflection of the likelihood of any other 100-spin session, as RTP's are set over many millions and probably billions of spins. So this 100 spin test is just for entertainment and insight purposes

Session RTP265%
Win FrequencyMedium 24/100
Biggest Base Game Win20x
Spins to Bonus13
Bonus Paid155.5x
Average Win Value over 100 Spins11.04x with Bonus, 4.76x Ignoring Bonus

The Spin Test criteria can be found at the bottom of the page

Test Comments

Despite not being a fan of this type of game and one to approach Thunderkick games with an air of caution, 12 Bolts of Thunder delivered in spades, with the bonus round hitting at just spin 13 of the test - The bonus was pretty impressive paying a 155.5x round which set me up nicely to complete the test with a huge 265% Session RTP - The hit frequency was still pretty good given the big bonus with 15x and 20x base game wins dropping in, thanks to the hammers landing, with 24 wins in all from the 100 spins. 

Steve Madgwick

Steve Madgwick


Steve is a confessed online slots fan and keeps his hand in the slot section of OLBG by undertaking all of our 100 spin tests, collecting the data and updating this section with the results

12 Bolts of Thunder Expert Review

Theme & Symbols
Bonus Features
Max Win (30,000)
Sounds & Music
RTP (96.15%)

Game Data

Collected by Andrej Trajkovski


Thor is one of the most well-known characters in Norse mythology; he is the God of lightning, thunder and storms. He is instantly recognisable by his thundering hammer, which is the basis of this brand-new slot game. It's all about the hammers here - when you play, you'll see that these make up the bulk of the features.

In addition to the Hammer symbol mentioned in the summary, you'll be able to play a fun Free Spins round. Here, there are 6-12 free spins and 'Hammer wins,' which take place during the bonus game. These Hammer wins upgrade each multiplier level on the Hammer Paytable. There are up to 5 upgrades available, and the top multiplier at the highest level is a whopping 30,000x the stake.

During this detailed 12 Bolts of Thunder slot review, you’ll be able to read about all aspects of this brand-new release, so let’s power on!

 Slot Review Game Data
Theme Mythology
RTP %96.15
Reel Style5x4
Stake Range£0.10 - £100
Max Win30,000x
Special SymbolsHammer symbol, Wild symbol & Bonus symbol
FeaturesHammer Wins & Bonus Round (Free Spins)
JackpotNo Jackpot

Graphics, Music, and Sound Effects

Key Features

Written by Slots Content Manager Jenny Mason

I've now covered the summary, intro, graphics, music, and sound effects. Next on the list, I’m going to explore the key game features of 12 Bolts of Thunder.

At OLBG we create slot games reviews that include up-to-date info about essential features such as the theme, paylines and reels, bet range, and bonuses. I’ll finish off the review by talking about my play experience, first impressions and expert verdict.

Theme – Mythology

The game is based on Thor's magical hammer, which is called Mjölnir in case you're interested. Thor himself doesn't make an appearance in this game; however, it's set in some otherworldly realm - perhaps Asgard, where the gods in Norse mythology resided. As befitting of a game set in a place where Gods are supposed to hang out, the colours are based on the blues of the sky, and you'll see plenty of fluffy white clouds. 

When switching to the altogether different realm... of the Bonus Game, the colours switch to pink, purple and orange hues, which gives a glow to the screen. The grid is eye-catching with dazzling colours, and the Hammer Paytable matches this design, so you can't miss it. On the grid, in order of value from the highest, you'll see number 7s, the word BAR, a bell and a lucky horseshoe. These are then followed by the standard symbols of, A, K, Q and J.


The 12 Bolts of Thunder slot game is made up of 5 reels and 4 rows to play with. 


There are 20 non-adjustable paylines where you can trigger wins.


Return to Player is most commonly referred to as RTP which you may have seen on slot sites. This is a way of measuring theoretically what percentage of players' stakes will be returned to them over the long term so it's an important measure. The higher the number the better for players, RTP should be around 96% or more. 12 Bolts of Thunder is slightly over the average at 96.15%.

Thunderkick use this RTP figure as a default value so if you shop around you’ll discover different rates. To save you some time, we’ve identified a few at some of the current popular UK online casinos and added them to our table below.

By the way, RTP is just one factor when deciding which site to play at. You should also think about payment options, game library, customer support and welcome bonuses and deals. Our casino reviews look at this info and much, much more.

All British Casino96.15Read Now
Fun Casino96.15
Read Now
Dream Vegas96.15
Read Now
Grand Ivy96.15
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Las Vegas Casino96.15
Read Now

If you fancy playing more than one game you should visit this page with the slot sites we recommend

Stake Range

There’s a wide bet range for the 12 Bolts of Thunder slot game which starts at £0.10 and goes right up to £100.

Max Win

The max win for the 12 Bolts of Thunder game is an impressive 30,000x your stake.

Wild Shape

The Wild symbol substitutes for all other paying symbols apart from the Bonus and Hammer symbols.

Free Spins

3 or more Bonus symbols trigger the Bonus Game, which features free spins. The number of free spins you receive depends on the number of Bonus Symbols landed. Hammer Wins during the bonus game will upgrade each multiplier level on the Hammer Paytable after payouts. The maximum of upgrades available is 5. The highest multiplier is 30,000x for 12 Hammer symbols at the highest level.


Like most slot games nowadays, the 12 Bolts of Thunder slot game doesn't have a jackpot element. If jackpots are your thing you should visit our page with the best jackpot slot games.

Play Experience & First Impressions

When launching the game for the first time it was aesthetically pleasing, but does it have the features to back it up? The gameplay is straightforward; the Hammer Paytable is key, so during the base game, you're hoping to see 4 or more Hammer symbols. A multiplier prize table is a tried-and-tested slot mechanic; you'll be familiar with it if you've played slots for a while.  The Hammer Win during the Bonus Game made things a bit more dramatic and exciting due to the sheer amount of hammers popping up on the screen. However, the features felt a bit flat to me, it was a bit too simple.

Expert Verdict

I had high hopes when launching the game for the first time, as it looked slick but it soon became apparent that the features were not particularly engaging. The storytelling side was weaker than it normally is for a Thunderkick game, too. It's almost like having 2 slices of bread and a slice of cheese there, but there's something extra needed to make it tastier - perhaps onion would work for this sandwich metaphor. A character to front the game would have been good too - characters seem to create a stronger theme in the slots world.  Seeing Thor wield his massive hammer on the grid might have worked well on the screen. Thunderkick's last release was Hellapenos which definitely had more meat on the bones (wow, the food references are rolling off my tongue today).

However, one huge silver lining is the max win amountof 30,000x your stake; this is Thunderkick's second largest amount to date, so that is worth shouting from the rooftops. 12 Bolts of Thunder is an uncomplicated game with a high volatility rating and a huge max win. If this is what you are searching for, you've come to the right place. If you are looking for something with a bit more pzazz this might not be the right title for you.

Editorial Information

The 12 Bolts of Thunder slot review was written by our slot game experts on the OLBG Expert team. Beginning with Jenny Mason our prime Slot reviewer who has 17+ years in online gambling, top UK brands. Expert in sports betting, slots, and bingo. Then Andrej Trajkovski, who has worked in the online gambling industry since 2013, playing and reviewing online slots and casinos daily for the past four years. 

The review is Fact Checked by William Westerlund, an online casino expert reviewing casinos and slots for over five years.  Steve Madgwick is our Editor-In-Chief with over 18 years of experience creating and managing high-quality sports betting and Casino content for OLBG, a self-confessed online slots fans who has played at 100's of the best slot sites online and completes the 100 Spin tests to keep his hand in.

William Westerlund

William Westerlund

Casino and slots editor

William Westerlund is an online casino expert who has been reviewing casinos and slots for over five years. He has attended numerous online gambling conferences and been featured as an expert in several publications. William is also an avid poker player.

👨‍🏫 Specialist Subjects🔬📚

🎰🍒🍀 William is a long-time industry expert and has helped OLBG with contributions to our casino content and online slots reviews content too.

Jenny Mason

Jenny Mason

Slots content manager

Jenny Mason has more than 17 years of experience in the online gambling industry and has worked for some of the UK’s top betting brands. She started at OLBG in 2014 and her role involves creating great content and looking after the marketing activity. Jenny is knowledgeable in all areas of online sports betting and has an interest in slots and bingo.

👨‍🏫 Specialist Subjects🔬📚

🎰🍒🍀 Jenny has become an expert with online slots completing hundreds of our various new slot reviews and creating and writing some of the slot articles found on site. She has become a firm fan of NoLimitCity and Hacksaw gaming slot in this process and always awaits the new releases with much anticipation

100 Spin Test Criteria

The 100 Spins test is undertaken on a demo slot, staking 100 spins at £1 per spin

Session RTP - Return to the player after 100 spins - Eg, A return of £45 from 100 spins is 45%, or a return of £107 is 107%

Win Frequency - A winning spins to spins frequency, higher frequency regardless of prize, is often more entertaining.

  • 0-10 Very Low
  • 11-15 Low
  • 16-30 Medium
  • 21-35 High
  • 36+ Very High

Biggest Base Game Win  - Highest single base game spin winning value

Spins to Bonus - How many spins were completed before the main bonus round was achieved

Bonus Paid - Value of bonus once complete

Time Taken  - How long did the 100 spins take to complete? OLBG Expert team

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