Rich Wilde and the Tome of Insanity slot has 5 reels and 5 rows, and it pays when you hit a cluster of at least 4 matching icons. The more icons in the cluster, the bigger the prize.
The game pays as follows for 4, 5, 6, 8, 9, or 10+ symbols in a cluster:
Skull: x2, x4, x8, x32, x50, or x100
Watch: x1.2, x2.4, x5, x18, x25, or x40
Tentacle: x1, x2, x4, x15, x20, or x30
Poison: x0.8, 1.5, 3, 10, 15, or 25
Purple gem: x0.4, x0.6, x1, x3, x4 or x6
Red gem: x0.3, x0.5, x0.8, x2, x3.2, or x5
Blue gem: x0.2, x0.3, x0.5, x1.6, x2.4 or x4
Green gem: x0.1, x0.2, x0.3, x1.2, x1.8 or x3
Book: Wild symbol, can open portals
Rich: Multiplier Wild (x2, x3, x4 or x5 in the base game, x2, x3, x5, x10 in free spins)
Yog-Sothoth: 2x2 Wild, walks the grid 3 times