d20
The Icosahedron (d20)
The Heart of Modern RPGs
The 20-sided die is the signature die of the Dungeons & Dragons game system and many other RPGs.
Ability Checks
Roll a d20, add your relevant ability modifier, and compare the total to a Difficulty Class (DC).
Attack Rolls
Roll d20 + Attack Bonus vs. the target's Armor Class (AC). Rolling a "Natural 20" is a Critical Hit.
Saving Throws
Used to resist spells, traps, or poisons. d20 + Save Modifier vs. Save DC.
Did You Know?
"The oldest d20s date back to Ptolemaic Egypt (300 B.C.), though they were likely used for divination rather than gaming."