Kovaalan vessels battle with Enterprise.
The Kovaalans are a race that inhabits the Delphic Expanse. They are very territorial; one of their claims is a nebula that houses a subspace corridor leading to the Xindi Council planet. They normally maintain one or two vessels in the nebula to deter trespassers.
In February 2154, when the NX class starship Enterprise attempted to travel through the corridor, the Kovaalans had increased their presence to six ships. Nevertheless, Enterprise made it through with the help of a future version of itself. (ENT: "E²")