Enormous armoured creatures able to travel along the mycelial network, one of which was used to navigate the USS Discovery's spore drive.
Space tardigrades are enormous armoured creatures resembling giant versions of Earth's microscopic tardigrades. They share a symbiotic connection with the mycelial network, which allows them to jump across vast distances in an instant, and they are extremely tough.
In Discovery, a tardigrade nicknamed Ripper was found aboard the USS Glenn. Captain Gabriel Lorca had it brought to Discovery, where it was used as a living navigator for the spore drive, suffering serious harm with every jump. Michael Burnham recognised its distress, and Paul Stamets took its place by injecting himself with tardigrade DNA, allowing the creature to be released.