Ten Essential Rules to Remember

1. Exceptions > General Rules

   • General rules apply unless something specifically says otherwise. Exceptions take precedence.

2. Round Down

   • Always round down when dealing with fractions, even if it’s 0.5 or higher.

3. Advantage & Disadvantage

   • Only apply advantage or disadvantage once per roll. If both apply, they cancel out.

4. Combining Effects

   • Different effects can stack, but effects with the same name do not. Use the most powerful effect.

5. Reaction Timing

   • Reactions occur after the triggering event unless stated otherwise. You can take only one reaction per round.

6. Resistance & Vulnerability

   • Apply damage modifications in this order: immunity, addition/subtraction, resistance, vulnerability. Multiple resistances or vulnerabilities of the same type don’t stack.

7. Proficiency Bonus

   • Your proficiency bonus can only be applied once per roll, even if multiple sources suggest otherwise. Doubling/halving only occurs once.

8. Bonus Action Spells

   • If casting a spell with a bonus action, you can only cast a cantrip (with 1 action) in the same turn.

9. Concentration

   • Starting a new concentration effect ends any ongoing concentration immediately.

10. Temporary Hit Points

• Temporary hit points do not stack. Choose which set to keep when you receive new temporary hit points.

Simultaneous Effects

Most effects in the game happen in a sequence. However, if two or more effects occur at the same time during a creature's turn, the player or DM controlling that creature decides the order in which the effects happen.