O regra opcional sobre flanqueamento (DMG, p. 251) diz:
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 descrição do Rogue assassino's Assassinar O recurso (PHB, p. 97) diz:
Starting at 3rd level, you are at your deadliest when you get the drop on your enemies. You have advantage on attack rolls against any creature that hasn’t taken a turn in the combat yet. In addition, any hit you score against a creature that is surprised is a critical hit.
Se estou flanqueando uma criatura, meu ataque é considerado um ataque surpresa?
Teve um debate ontem sobre se Assassinate pode ou não ser usado a cada rodada ou apenas na primeira rodada de combate 'Surprise'. Nós decidimos ou o último. Isso está correto?