Weight: ½ lb.
Estimated Value: 6,000 gp
This figurine of wondrous power is an ebony statuette of a horsefly, small enough to fit in a pocket. If you use an action to speak the command word and throw the figurine to a point on the ground within 60 feet of you, the figurine becomes a giant fly. If the space where the creature would appear is occupied by other creatures or objects, or if there isn't enough space for the creature, the figurine doesn't become a creature.
The giant fly is friendly to you and your companions. It understands your languages and obeys your spoken commands. If you issue no commands, the creature defends itself but takes no other actions.
The giant fly exists for up to 12 hours and can be ridden as a mount. At the end of the duration, the creature reverts to its figurine form. It reverts to a figurine early if it drops to 0 hit points or if you use an action to speak the command word again while touching it. When the creature becomes a figurine again, its property can't be used again until 2 days have passed.
Source: DMG p169