This guide discusses the Mental slot's RTP versions, max win and UK stake limit, and the way the game differs when you play in Great Britain. Most pages regarding Mental list a single RTP value. Nolimit City actually provides the game in two versions, and the casino chooses which one you use. The gap is small for each spin but measurable across a session.
The game in brief
Mental is a horror slot from Nolimit City, launched on 31 August 2021 and taking place in a sinister asylum, according to the provider. It features five reels and three to five rows. The provider labels its volatility as Extreme (10), which is the highest on its scale. The top payout is 66,666 times the bet, and the provider's simulation of 10 billion spins puts the odds of achieving this at around 1 in 18 million spins. The round finishes immediately if the maximum is hit. Nolimit City offers free play of the game on its own platform.
Two RTP versions, chosen by the casino
According to Nolimit City's game sheet, Mental is "available with dual RTP setup":
- Standard version: 96.08%, found under the game ID Mental
- DX1 version: 94.20%, found under the game ID MentalDX1
Both versions of the game are identical. A different maximum payout or a distinct bonus-buy return for DX1 isn't listed on the provider's sheet. The feature list and the 66,666x cap apply to both.
The RTP is listed as 96.06% in at least one common listing. That number is incorrect. Both the game sheet and the game page from the provider state 96.08%.
Nolimit City's more detailed game sheet also divides the return into two sections: 58.16% is from the main game and 37.93% is from free spins. More than a third of the return arrives through the bonus rounds. This is important for a game where free spins trigger roughly once in 216 spins.
How to check which version you are playing
The provider names both versions, but doesn't specify which casino uses which. Check the paytable or the information screen within the game to find the listed RTP. The standard version is the one with 96.08%. DX1 is the one with 94.20%. A casino with a licence in the United Kingdom may also list the version it runs in its own game details.
What the gap costs in money
In the long term, play costs the house edge multiplied by the amount staked, with the house edge being 100% minus the RTP. This results in 3.92% for the standard version and 5.80% for DX1. These figures are long-run averages rather than forecasts. On a game this volatile, a single session can finish well above or below these values.
| Play | Total staked | Average cost at 96.08% | Average cost at 94.20% |
|---|---|---|---|
| 100 spins at £0.20 | £20.00 | £0.78 | £1.16 |
| 100 spins at £1.00 | £100.00 | £3.92 | £5.80 |
Across 1,000 spins at £1.00, the 94.20% version costs an average of £18.80 more than the 96.08% version. This amount is taken from your stake via slightly lower returns. It is never displayed as a fee.
How the features work
Mental employs several mechanics that stack:
- Fire Frames show up in 1 to 13 random spots and divide the internal symbol in half.
- Enhancer Cells activate if four or six Fire Frames land. These provide boosters like xWays, xNudge and xSplit.
- xWays turns a symbol into a stack consisting of that same symbol.
- xSplit divides symbols to its left and subsequently becomes wilds.
- xNudge wilds shift to occupy a reel, increasing their multiplier by one per nudge.
- Dead Patient: hitting two Dead Patient symbols gives a chance of a random multiplier between x5 and x9999 on a Patient symbol.
- Mental Transform, a feature that transforms symbols, triggers each time a Spider symbol lands.
Nolimit City provides a hit frequency of 34.19%, meaning about one in three spins results in a win. A win of 100 times the bet occurs roughly once every 831 spins.
The three free spins rounds
- Autopsy Freespins: three Scorpion symbols. Fire Frames remain sticky, and the round can upgrade to either of the other two.
- Lobotomy Freespins: three Scorpions and a Spider. The Spider remains sticky and gives Mental Transform on each spin. A Dead Multiplier moves to a Patient symbol. This round can still upgrade to Mental Freespins.
- Mental Freespins: three Scorpions and two Spiders. Spiders remain sticky, and the Dead Multiplier doesn't decrease.
Mental under Great Britain's slot rules
It is legal to offer online slots in Great Britain, and Mental is one such game under Gambling Commission regulations. The materials from the provider describe the game as it is sold globally. Several parts of that description do not apply to a British player.
Stakes
The provider's sheet indicates a betting range from €0.20 to €70. In Great Britain, the Commission limits the stake per game cycle:
- £5 for players 25 years or older (effective from 9 April 2025)
- £2 for players between 18 and 24 (effective from 21 May 2025)
Your available range goes from the minimum bet up to £5 or £2, based on your age. You cannot play the top end of the provider's range.
The bonus buy
You can use the Nolimit Bonus feature buy to enter a bonus round immediately for between 80 and 1,000 times your base bet. The cost of a buy is included as part of your stake for that game cycle under the cap. Even at 80 times the lowest allowed bet, the cheapest buy costs well over £5. In practice, no feature buy in Mental stays within either cap. A British player can only access the free spins rounds by landing the Scorpions. Nolimit City's own sheet mentions that the buy might be removed in some regulated markets.
Play speed and presentation
- No autoplay. You must trigger every spin manually.
- No turbo, quick spin or slam stop. All settings that reduce the duration before a result appears are disabled.
- At least 2.5 seconds have to elapse between the beginning of one spin and the beginning of the following one.
- No win celebrations for returns that don't beat your stake. With a hit frequency of roughly one in three, many of Mental's wins return less than the amount bet. These should be displayed without the animations and sounds reserved for real wins.
On an extreme-volatility game like this, it is useful to establish a budget before you play and stop once you hit it.