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All aboard! The casino space station is about to depart on a journey into the deep reel universe on the slot from Elk Studios. Io is after Cygnus the second release in their Gravity Series, taking you on an exploration tour into the unknown in search of new promising lands and wins of up to 5,000 times your bet. Symbol avalanches and the gravity mechanic will make every spin a unique experience, clearing winning symbols and expanding the game window as you venture deeper into space. Extra features including Charged Wilds, Lasers, Wild Forge with progressive multipliers and a free spins round will help you navigate through up to eight rows and 262,144 ways to win.

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100% Refund Bonus, up to £111 + 100 Bonus Spins
Main termsFull T&C Apply
New Customers Only
Deposit Bonus100% Refund Bonus, up to £111 + 100 Bonus Spins
Extras77 Bonus Spins on Starburst or Book of Aztec
No Deposit Offer23 Bonus Spins on Starburst or Book of Aztec
Bonus availableValid until further notice
Time to meet requirements30 days
OperatorL&L Europe Ltd
Max bet size£5
Max Cashout
Deposit bonusNo limits
ExtrasNo limits
No deposit max cashout100
Wagering Req.
Deposit Bonus60 X Bonus
Free spins40 X Bonus
Sticky BonusNO
18+, new players only. T&Cs apply. 23 Bonus Spins on registration. Min. dep. £10. Max. Refund Bonus 100%/£111 + 77 Bonus Spins. Wager 60x bonus & 40x spin winnings. Max. bet £5. Max. cashout no-deposit spins £100. No Skrill & Neteller. Gamble responsibly. www.BeGambleAware.org.

Slot Details

Io is a cascading video slot with six reels, 4 – 8 rows and 4,096 to 262,144 ways to win. Pays are awarded for three to six matching symbols on adjacent reels starting from the leftmost. You can journey to the faraway planet on mobile or desktop from 0.20 to 100 coins. The game has high volatility (8/10) with an RTP of 96.00%. You can use Betting Strategies and Autoplay to customize your play patterns and set up 10 to 100 consecutive spins.

Loading the game will see you stepping into the casino space station that will take you on the slot journey through the solar system. Flanked by flashing displays of existing Elk Studios slots, stand two massive pillars that will hold the pay symbols as they avalanche onto the screen, all illuminated from the bottom by a giant beam light. The star-studded sky view in the background will turn into flashing warp streaks on teaser spins.

The paytable includes eight regular symbols, starting with the card royals from J through to A at the low end, awarding 0.2x to 0.35x your stake for a single six of a kind. The premiums are classic slot machine symbols – blue stars, green 4-leaf clovers, pink diamonds and red 7s. Hit six across the reels to win 0.6x to 5x your bet. The game has three different wilds (more to that shortly), substituting for all regular symbols and yielding as well 5x stake when six land on the reels. A planet-shaped icon marked with ‘Bonus’ acts as the scatter.

Avalanche and Gravity Slide Mechanic Explained

Being part of the Gravity Series, Elk Studios built the main part of the gameplay on Io again on two reel mechanics that will see you progressing from the default 6×4 format and 4,096 ways to a giant grid with up to 8 rows and 262,144 ways to win. Most players will be familiar with the Avalanche mechanic. where at the start of a spin sequence symbols drop from the top to fill the reels. Any winning combos will explode after they are paid to make space for new symbols to avalanche into place.

This is the moment where the Gravity mechanic comes into play. Usually, any remaining symbols would drop vertically towards the bottom and new symbols would avalanche into the empty spaces. On Io, however, the remaining symbols fall first vertically and then slide to the left or right repeatedly based on gravity until they land in a resting position where they are unable to move any further. Should the movements create new winning combos, then they will explode as well and the sliding process is repeated.

The game will avalanche new symbols onto the grid only after no more wins occur through the sliding process. Symbols drop into the empty spaces while also adding an additional row at the top and thus gradually increasing the ways to win from four rows and 4,096 ways up to eight rows with 262,144 ways. The game window will stay expanded until the end of a round and will then reset to the default 6×4 format before the next spin sequence. All wins from a sequence are accumulated and paid in one amount.

Io Slot Features

Elk Studios has shown throughout their Gold as well as Gravity series an immense creativity when it comes to reel modifiers. Each of the slots has distinct features that will help players to keep the series of winning avalanches going and thus score multiple wins within a spin sequence. On Io, much of that falls to not one but three different wilds. You will see the standard wild doing its usual substitution duties and disappearing once it is part of a winning combo. The other two, called Wild Forge and Charged Wilds, will stay on the screen for multiple avalanches, providing extra potential for consecutive wins within a spin sequence.

The Charged Wild appears marked with four lives. It will stay on the screen throughout a spin sequence and gravitate through the avalanches and the sliding process. One life is deducted every time the wild is part of a winning combo. The Charged Wild will disappear with the next avalanche once all four lives have been used or when a spin sequence concludes.

The Wild Forge has made already a similar appearance on Voodoo Gold and Tahiti Gold, however, on Io it comes with an additional twist. A golden portal-like icon may land on any reel and will stick in place as long as it cannot fall vertically. Any empty space below it after a winning avalanche is cleared will be filled with a wild symbol. A progressive multiplier increases by x1 every time the Wild Forge is part of a winning combo, no limits. The forge symbol itself does not count as a wild symbol until it falls to the bottom where it will turn into a multiplier wild with the accrued multiplier from the previous avalanches. In the base game, it will disappear after that or whenever a spin sequence ends.

The Laser feature is triggered when one or two Omega-style symbols land anywhere on the reels and no more wins occur. A single Laser symbol will create a beam in one direction – diagonally, horizontally or vertically – and remove itself and all symbols crossed by the beam except any type of wilds or scatters, letting new symbols drop down to potentially create more winners. Two or more lasers will project their beams in a similar fashion and should the beams intersect then the laser icons and all symbols up to the intersection point will turn into wild symbols for the current avalanche. In both cases, the Laser symbols will disappear once the modifier has been applied.

Having three to six scatters in view at the end of a spin sequence will trigger 7 to 15 Free Spins, which can be indefinitely retriggered. The free spins are played on the maximum game window with eight rows and 262,144 ways to win. Any Charged Wild, as well as Wild Forge symbols with their accrued multiplier, will be collected at the bottom between free spins and will remain on the screen for the next free drop only. The Charged Wild will lose a life between free spins. More than one multiplier wild from the Wild Forge will be added, not multiplied by each other.

Final Verdict

Reviewing a slot from Elk Studios feels often like we are reel explorers on a discovery tour. The team is highly creative when it comes to visuals, modifiers and features, surprising us every time with either completely new mechanics or adaptations of existing ones. It was no different when we loaded the Io slot for the first time. We wonder though how much shorter a title for a game could be; with just two vowels we decided to bold the name on each occasion in this review as otherwise readers might think it is a typo.

Rather unsurprising but not really disappointing is the max win potential which peaks at the Elk usual of 5,000 times your bet. By far, not the highest we have seen on other slots but something every avid slotting fan will happily take home any time of the day.

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