Makhaira Aquamarine is a 4 star Claymore obtained from Weapon Event Wishes in Genshin Impact 3.1.
Desert Pavilion
The following effect will trigger every 10s: The equipping character will gain 24/30/36/42/48% of their Elemental Mastery as bonus ATK for 12s, with nearby party members gaining 30% of this buff for the same duration. Multiple instances of this weapon can allow this buff to stack. This effect will still trigger even if the character is not on the field.