Special Symbol games use one marked icon to trigger extras, boost wins or change the reel state. The 64-game catalogue favours clear mechanics, free demos and quick comparison before real-money play.
Special icons sit outside normal line-pay logic. One symbol may trigger Free Spins, expand during a bonus, collect prizes, add a multiplier or start a respin round. I treat the label as broad, not one fixed mechanic. Popularity comes from visible cause and effect: hit the marked icon, then the slot changes state.
Names vary by studio. Play'n GO often uses expanding bonus symbols, while 3 Oaks Gaming (Booongo) favours prize-style icons and hold rounds. NGM Game appears strongly in the catalogue too. Same family, different maths. The weak point is clarity; some paytables explain the icon well, others hide too much behind short help screens.
How the icon changes play
Marked symbols usually affect four areas: trigger, multiplier, frequency and volatility. A Scatter-type icon starts a bonus. A special Wild substitutes or expands. A prize icon can lock on reels inside Hold and Win. I prefer designs where the paytable states the trigger count, because vague wording makes bankroll control harder.
Games worth testing first
Book titles give the cleanest read. Book of Dead has a special expanding symbol during Free Spins, with 96.21% RTP on its common version and a 5,000x cap. Rise of Olympus and Moon Princess use character or symbol powers with stronger feature focus. Both suit demo testing before staking.
Ceiling-led tests sit with prize-symbol games. Sun of Egypt 3, 15 Dragon Pearls and Aztec Sun rely more on bonus icons than steady base hits. Reactoonz adds special charged symbols inside Cluster Pays logic. I would run 80 to 120 demo spins at minimum stake, then judge pacing.
RTP and variance impact
RTP averages 96.17% across the category, a fair number for UK-facing online slots. Max win averages 6,483x, but I would not use that as a selection rule; caps vary too widely between book games, cluster games and hold-style bonuses. Trigger rarity matters more. Low-hit versions drain balance between features, especially at high stake sizes.
Provider spread and licences
Provider choice is concentrated. NGM Game, Play'n GO and 3 Oaks Gaming (Booongo) lead the set, so the catalogue has recognisable patterns rather than huge mechanical diversity. Casinos licensed by UKGC or MGA can host these games, but UK rules still block autoplay and Bonus Buy style shortcuts.
FAQ
What is a special symbol slot?
A special symbol slot uses a marked icon with extra rules beyond normal paylines. In Book of Dead, the chosen symbol can expand during Free Spins; in Reactoonz, charged icons affect the Cluster Pays feature.
On how many games is it available?
The category currently lists 64 games. The strongest provider presence comes from NGM Game, Play'n GO and 3 Oaks Gaming (Booongo).
Can you play these games for free?
Free demos are the sensible starting point, with no sign-up needed on the catalogue page. I would test Sun of Egypt 3, 15 Dragon Pearls and Aztec Sun in demo mode before real stakes.
What is the average RTP here?
The average RTP is 96.17% across the category. Some individual games, such as Reactoonz and Moon Princess, can differ by version, so the in-game paytable remains the final check.
Do special symbols increase volatility?
They often do, especially when the icon triggers a deep bonus or a prize-lock round. Free Spins, expanding symbols and Hold and Win style features can shift more value into fewer events.
All our content is written by our editorial team and checked before publication. We play the games ourselves, verify licences and withdrawal terms, and update every review as soon as something changes.
Under the supervision of Editor-in-Chief Mark Rylance
