A Brancher engages Starfleet ships in 2409
Branchers, sometimes called Crystalline Entities, are a race of Cosmozoan, crystalline lifeforms. The most well-known Brancher is known only as the Crystalline Entity, which is infamous for destroying multiple Federation colonies. The USS Enterprise-D made first contact with the Branchers in 2364 when they encountered the Crystalline Entity, who was working with Lore to devour the humanoids aboard Enterprise. (TNG episode: "Datalore"; TTN novel: Orion's Hounds)
In 2378, the USS Theseus, under guidance from the Prophets, travelled to the Hephaestus Nebula, populated by hundreds of Branchers, arriving in time to see them all perish at the hands of Kahless and his godkiller array. (ST - Godshock comics: "Part 1", "Part 5")
Shortly afterwards, Worf and Spock visited the ruins of Kazis IX, a world Kahless had killed to recharge his weapon, and discovered a high antiproton signature, the same kind a Brancher left after feeding. This led Spock to conclude that Kahless had somehow absorbed the powers of the Branchers he had slain. This led the two to recruit Lore for his experience with Branchers. (ST comics: "Defiant, Issue 1", "Defiant, Issue 2")
The USS Titan encountered more Branchers in the early 2380s. They learned more about the creatures, including their name. The name 'Brancher' was given to them by the Pa'haquel, who live in a region of active star formation in which many cosmozoans, including the Branchers, inhabit. Generally the Pa'Haquel use their skymounts to destroy the Branchers, to keep them from annihilating inhabited worlds, but due to negotiation with Titan's crew and the Star Jellies, the Pa'Haquel became herders of the Branchers, using graviton beams copied from Starfleet technology. (TTN novel: Orion's Hounds)
In 2409, another Brancher entered Federation space and engaged a fleet of Federation starships. This Brancher was capable of launching shards off of itself which were individually capable of engaging a starship. Additionally, if the shards shattered, each of the original pieces would return to the main entity and heal it. (STO mission: "Crystalline Catastrophe")