Flanking
Optional rule: allies on opposite sides of an enemy gain advantage on melee attacks. Many tables modify or skip this rule for balance.
Flanking (Optional Rule)
Flanking is an optional rule from the Dungeon Master's Guide that rewards tactical positioning with easier attacks.
How It Works
When two allied creatures are on opposite sides of an enemy (directly across from each other through the enemy's space on a grid), both allies have advantage on melee attack rolls against that enemy. The allies must be able to see the target, and neither can be incapacitated.
Grid Requirements
On a standard square grid, flanking occurs when two allies occupy squares on directly opposite sides of a creature (e.g., one to the north and one to the south, or one to the northeast and one to the southwest). On a hex grid, the allies must have a straight line drawn between their centers that passes through opposite sides of the target's hex.
Balance Considerations
Many DMs choose not to use flanking because advantage is very powerful and easy to achieve with this rule, which can devalue class features and spells designed to grant advantage. A common house rule alternative is to grant a +2 bonus to attack rolls when flanking instead of full advantage.
Interaction with Advantage
Since advantage does not stack with itself, flanking provides no additional benefit if the attacker already has advantage from another source.