DnD5e Rules to Argue About: Flanking!

There are a variety of DnD5e rules that are either not entirely clear, ambiguous, or non-existent. Here are some, starting with the optional Flanking from the 5e DMG:

Optional Rule: Flanking

DMG p.251

If you regularly use miniatures, flanking gives combatants a simple way to gain advantage on attack rolls against a common enemy.

A creature can’t flank an enemy that it can’t see. A creature also can’t flank while it is incapacitated. A Large or larger creature is flanking as long as at least one square or hex of its space qualifies for flanking.

Flanking on Squares. When a creature and at least one of its allies are adjacent to an enemy and on opposite sides or corners of the enemy’s space, they flank that enemy, and each of them has advantage on melee attack rolls against that enemy.

When in doubt about whether two creatures flank an enemy on a grid, trace an imaginary line between the centers of the creatures’ spaces. If the line passes through opposite sides or corners of the enemy’s space, the enemy is flanked.

Flanking on Hexes. When a creature and at least one of its allies are adjacent to an enemy and on opposite sides of the enemy’s space, they flank that enemy, and each of them has advantage on attack rolls against that enemy. On hexes, count around the enemy from one creature to its ally. Against a Medium or smaller creature, the allies flank if there are 2 hexes between them. Against a Large creature, the allies flank if there are 4 hexes between them. Against a Huge creature, they must have 5 hexes between them. Against a Gargantuan creature, they must have at least 6 hexes between them.

A creature can’t flank an enemy that it can’t see. A creature also can’t flank while it is incapacitated. A Large or larger creature is flanking as long as at least one square or hex of its space qualifies for flanking.

Alternative Flanking

Flanking adds a +2 bonus to attack rolls. 

Enough to negate armoured combative shield. I commonly would use this rule until Cody at Taking20 laid out the math.

Flanking (Taking20 Alternative)

When a creature and an Allie are adjacent to an enemy and on opposite sides or corners of an enemy’s space they gain a +1 to attack rolls.

A creature that is larger than an enemy and its size overlaps two corners of a target gain this benefit.

ConFusion

Mathematically, the Taking20 alternative to Flanking (+1 to attack rolls), is enough of an incentive to get PCs and NPCs to use it – but doesn’t make it an overpowering ability that Advantage gives (larger change to hit, doubling critical chances, etc.).

Resources:

Keith Ammann, The Flanking Rule: Why Many DMs Hate It and Why I’ll Still Use It, (2018/01/15), https://www.themonstersknow.com/965-2/

Taking20, Flanking Response to XP to Level 3 | Dungeons and Dragons 5e, (2019/07/02), https://www.youtube.com/watch?v=T_T1MLB2nJk