Definition
A mystery bonus is a promotion where the reward is randomised and revealed on claim - a spin-the-wheel, a scratch card, a "mystery box" that resolves into free spins, bonus funds, cashback, or a small prize of unknown value until opened. It is a gamified delivery wrapper around ordinary bonus types, used to make claiming feel like a mini-game and to add a variable-reward element that increases engagement with the promotion.
The expected value of a mystery bonus is whatever the underlying reward distribution averages to, minus the usual terms (wagering, caps, eligible games) on whatever is awarded. The randomised reveal does not add value; it repackages a bonus of a given expected cost in a form designed to be more compelling to claim.
In context
For affiliates, mystery bonuses are a common promotion type where the gamified wrapper can obscure modest underlying value, so content should describe them plainly: it is a random reward from a set of ordinary bonus types, the reveal mechanic is presentation not value, and whatever is awarded comes with its normal terms. If the possible outcomes and their rough odds are published, a review can report them; if not, content should note that the value is unknown until claimed and typically modest.
The responsible-gambling angle is that the mystery/reveal mechanic is a small variable-reward loop layered onto a promotion, and content should not amplify the "what will I get?" excitement or present mystery bonuses as a reason to engage more. It should treat them as a delivery style for standard bonuses, apply the same honest-value framing (report the terms on whatever is awarded, don't rank by the top possible prize), and keep age-gating and responsible-gambling messaging.
Where a mystery bonus requires a deposit or a wager to claim, that should be stated. For affiliate-facing content, the framing is that mystery bonuses are gamified packaging around ordinary rewards, that the randomised reveal adds engagement not value, and that they should be covered with the same terms-focused honesty and safer-gambling framing as any bonus.
Worked example
An affiliate's review describes an operator's weekly mystery bonus as a scratch card that reveals one of free spins, small bonus funds, or cashback, each with standard terms. It notes the reveal is presentation, not added value, that the outcome is typically modest, and that it requires a qualifying deposit.
Age and responsible-gambling messaging are present.
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