All equippable items that raise or lower the Adept's power of the Venus element independently from and in addition to how many Venus Djinn the Adept has Set onto him or her. As of The Lost Age there is no equipment that lowers Venus power.
“The Warrior's Helm is a Helm-class piece of armor found in Golden Sun. It is found in a treasure...Warrior's Helm
“A Spirit Armlet is a Bracelet-class hand armor found in Golden Sun and Golden Sun: The Lost Age...Spirit Armlet
“A Planet Armor is an Armor-class piece of armor found in Golden Sun: The Lost Age. It is...Planet Armor