Book of Monsters Slot by Pragmatic Play

The gamble phase before free spins is the defining choice. After triggering the bonus, the game assigns a random paying symbol as your designated FAT symbol - could be a low-value royal, could be one of the seven monsters. You see what you got and decide: accept it, or gamble for a higher-paying symbol. Win the gamble, your FAT upgrades one tier. Lose, and the entire bonus round disappears. No consolation prize, no partial payout. You can keep gambling multiple times, pushing for the top monster, but each attempt risks everything.

Inside the bonus, that FAT symbol starts at 1x1 and grows through symbol collection. Every matching symbol that lands elsewhere on the 7x7 grid feeds a meter. Thirty collected symbols push the FAT to 2x2, then another 27 for 3x3, 24 more for 4x4, and so on down to just 12 needed for the final jump to 7x7. Each size upgrade awards 1 to 3 extra spins. A full-grid 7x7 FAT symbol means 49 connected symbols in one cluster - but reaching that takes 129 total collections across the round, so most runs top out somewhere around 3x3 or 4x4.

Base game drops random oversized symbols onto the grid without any collection system. A 5x5 block of the same symbol just appears, creating an instant 25-symbol cluster. These FAT symbols range from 3x3 up to a full 7x7, and they show up on any paying symbol. Cute monsters in a cave backdrop, bright colors, nothing dark about the theme despite the name.

The ante bet doubles your stake and gives a 7x higher trigger chance, dropping the requirement from 4 Bonus symbols to 3. It also locks out the 100x buy option, so you pick one shortcut or the other. The 5,000x cap keeps things grounded for a grid this size.