Mazarite ships that hunted Enterprise to recover the Vulcan ambassador V'Lar in Fallen Hero, forcing the starship past warp five.
Mazarite ships were vessels from the planet Mazar. In Fallen Hero, Enterprise was ordered to collect the Vulcan ambassador V'Lar, who had been expelled from the planet after being accused of misconduct, and take her to a waiting Vulcan cruiser.
A Mazarite ship opened fire to get her back, and Enterprise disabled its engines and escaped. Three more ships pursued, and Enterprise had to push beyond its rated speed of warp five to outrun them. V'Lar's expulsion turned out to have been part of an operation to expose corruption on Mazar.