Blackberry leaves have been used in various spiritual and ritual practices due to their symbolic and medicinal properties. Some of the ways blackberry leaves have been used in magic include:

Protection: Blackberry leaves can be added to protective sachets or charm bags to provide spiritual protection and ward off negative energies.

Healing: Blackberry leaves have medicinal properties and are used to make teas or tinctures for physical and emotional healing.

Divination: Blackberry leaves can be added to herbal blends for divination practices, such as scrying or other forms of divination.

Manifestation: Blackberry leaves are sometimes used in manifestation rituals to bring abundance and manifestation of desires.

Here is a simple manifestation spell using blackberry leaves:

Gather a few dried blackberry leaves and a small piece of paper.
On the piece of paper, write down what you wish to manifest. This could be a specific desire, goal, or dream.
Fold the paper and place it in front of you.
Light a candle and place it beside the paper.
Hold the blackberry leaves in your hand and focus on your intention for manifestation. Visualize your desire already being fulfilled.
Repeat the following incantation: "Blackberry leaves, bring to me, What I desire, so mote it be."
Place the blackberry leaves on top of the folded paper, letting the candle burn until it goes out on its own.
Carry the paper with you or place it in a special location where you will see it every day to keep your manifestation in mind.

For returning evil back to a person doing you harm:

Carve the name of your enemy into a Black Image Candle. Place the candle on a red handkerchief, pour some black salt over it, and wrap it up with some Blackberry leaves. Hit it with a hammer a few times then call out the person's name and what you want to return back to them.