The Garnet Rod was an item carried by Sailor Pluto. She primarily used the Garnet Rod to perform the attack Dead Scream, but it also functioned as a key of sorts to the Space-Time Door. Her talisman, the Garnet Orb, sat atop this Rod.
Sailor Pluto still had access to the Garnet Rod even in her civilian form. In the manga, it protected her from the Tellun she was analyzing, and in the anime, she used it to show the Inner Senshi a vision of the Silence.
There were inconsistencies with how the Garnet Rod appeared in the anime, in that there were sometimes round yellow gems decorating the heart-shaped arch at the top and sometimes there were not, and even when they were present the number of gems changed.