Legends of Belerath
Barbarians, Fighters, Monks, Rogues, and Warlords have the ability to apply a special condition called a “mark” to a target. After hitting a creature with a melee attack made as part of the attack action, you may choose to mark that creature as a bonus action. A mark lasts until the marking creature or the target dies, until the target is no longer within reach of the marking creature, until the marking creature makes an attack that does not include the creature, or until the target is marked by a new creature. New marks always supersede old ones, and a creature may only be affected by one mark at a time.
Multiclassing: A character may only use the mark of the class in which they have invested the greatest number of levels. If a character’ has multiple martial classes tied for a plurality of levels, they may use the mark of any of those classes. If a character has invested a plurality of their levels into a spellcasting class, they do not have access to any marks at all.
Barbarian: If a creature marked by you makes an attack that does not include you as a target, you may make an opportunity attack against it. Opportunity attacks against a marked creature always count as critical hits, but do not cause lingering injuries.
Fighter: You may make an opportunity attack against a creature marked by you without expending a reaction once for every five feet it moves through your reach.
Monk: If a marked creature moves out of your reach, you may, after taking your regularly allowed opportunity attack against them, shift up to your movement speed to follow them. You may only move toward the marked creature, and if possible must end your movement within 5 feet of them. This movement does not provoke opportunity attacks.
Rogue: On subsequent turns after marking a creature, you may deal your sneak attack damage against the creature if you hit with an attack even if you would not usually be able to.
Warlord: If a creature marked by you makes an attack that does not include you as a target, you and any of your allies within reach of the triggering creature may make an opportunity attack against the creature without expending a reaction.