Beacon
Beacon is a trait in Symphony of War. It is a Unit Trait that provides a 25% of the amount of healing to this unit when another unit in the squad is directly healed.
Strategies
Beacon is good for units that you want to prioritize on healing, such as the squad leader or the main damage dealer in the squad. If you have multiple of Beacon tomes, it's also a good idea to give 3 of them to your front row units to make sure they will constantly get healed.
Beacon can be used to great effect in Lysander's or Queen of Dragons' squads since they heals all units in the squad. Beacon means that the unit will gain a lot more healing from all the other units in the squad as well.
Obviously, never use this trait to a unit in a squad that has no healer. This trait is also useless for Risen units, as they can't be healed. The trait also has no effect from artifacts, like Everlasting Potion and Belinda's Field Kit.