Myrmidon (5e Creature)
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Medium humanoid (any race), any alignment
Swordfaire. The myrmidon gains a +1 bonus to attack rolls when it attacks with a sword (included in the attack). On the myrmidon's turn, it can use its reaction to assume a parrying stance, granting it a +1 bonus to its AC until the start of its next turn or until it is disarmed. Additionally, it has advantage on opportunity attacks with a sword.
Longsword. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d8 + 1) slashing damage.
Vantage. When a creature makes a melee attack against the myrmidon while the myrmidon is at or below its hit point maximum, the myrmidon may make an opportunity attack against the attacker. This opportunity attack occurs before the triggering attack.