Reference

Actions, combat rules, conditions, skills, feats and languages. Search by name.

During play

Actions Every combat action and what it does: Attack, Dash, Disengage, Dodge and more.

Conditions Every condition and what it does to a creature

Combat Rules Cover, advantage and the core combat rules

For your character

Feats Character feats from every source, with their prerequisites.

Skills Skills and the abilities behind them

Optional Features Eldritch invocations, maneuvers, metamagic and fighting styles

Languages From Common to Abyssal, with their scripts

Deities Gods by pantheon, with alignment, cleric domains and symbol

Combat Rules

Darkness

Source: XPHB

An area of Darkness blocks normal vision entirely. A creature in Darkness is heavily obscured, unless it has Darkvision or another way to see without light.

Attack rolls against a creature that can't be seen have disadvantage, and that creature's attack rolls have advantage.

Casting a spell that requires seeing the target usually isn't possible in Darkness unless the caster can see through it in some way.