After purchasing the second Hero, the $ icon appears on the home screen. This brings up a screen for the 4 Optional In-App Purchases. If you have made any purchases before and have switched devices, clicking Restore Purchases found under options, will restore any previously purchased items. A Reward Token can be redeemed by clicking on the Store button while a ! is present.
Merchant: The Frozen Tome
Unlocks the first expansion. Included is a new region, New lvl 51 Skills, Level cap raised to 60, New Hero Bard, New Prestige level, an extra inventory page, 2 more Hero slots, New theme and Merchant skin, Xp and Quest Speed events, and bug fixes!
This costs $2.99 USD.
Watch a short Ad and receive a free Reward Token. There is a limit to how many videos may be watched a day, but it is set by the Ad company and not the game Dev.
There are 3 other things that can be purchased through the App. Theme customization, Crafter unlocks, and Inventory Slots.
Theme customization can be accessed by clicking the top left button on the home screen. See Theme for examples. This unlocks 10 additional Skins and 6 Themes. You can freely change both Skins and Themes after unlocking. This costs $2.99 USD.
Instead of paying gold to unlock the Jeweler and Enchanter you may optionally pay with real-world money. The Jeweler may optionally be unlocked for $0.99 USD while the Enchanter may optionally be unlocked for $1.99 USD.
Unlocks an additional 16 Inventory Slots. Found under the Stock menu. This may be purchased four times in total. This costs $0.99 USD ea.