Idunn is a Norse goddess who is associated with youth, beauty, and vitality. She is considered to be the keeper of the golden apples of immortality, which are said to keep the gods young and strong. Here are some offerings, incantations, divinations, stones, herbs, and items that can be used when working with Idunn:

Offerings:

Apples: Idunn is the keeper of the golden apples, so offering her apples is a fitting tribute.
Honey: Honey is associated with sweetness and vitality, which are qualities that Idunn embodies.
Flowers: Idunn is associated with spring and new growth, so flowers are a good offering.
Milk: Milk is a symbol of nourishment and life, and can be offered to Idunn as a way of honoring her role as a giver of vitality.
Incantations:

"Idunn, keeper of the golden apples, grant me the gift of youth and vitality."
"Idunn, goddess of spring, bring new growth and renewal into my life."
"Idunn, mistress of the orchard, bless this apple with your divine energy."
Divinations:

Apple divination: Cut an apple into nine pieces, then ask a yes or no question. Take a bite of each piece, and if the ninth piece is sweet, the answer is yes.
Flower divination: Pick a flower, and the number of petals on it can be used to indicate a message.
Milk divination: Pour milk into a bowl, then swirl it around while focusing on your question. The shapes that form in the milk can provide insights into your situation.
Stones:

Emerald: Emerald is a stone of youth and vitality, and is associated with the energy of spring.
Amber: Amber is a symbol of life and vitality, and can be used to connect with Idunn's energy.
Citrine: Citrine is a stone of joy and happiness, and can be used to invoke Idunn's uplifting energy.
Herbs:

Peppermint: Peppermint is associated with youth and vitality, and can be used to honor Idunn's energy.
Rose: Rose is a symbol of love and beauty, and can be used to connect with Idunn's feminine energy.
Lavender: Lavender is a calming herb that can be used to invoke Idunn's peaceful energy.
Items:

Golden apples: Golden apples are a symbol of immortality and can be used as a talisman to connect with Idunn's energy.
Spring flowers: Spring flowers can be used as offerings or as decoration when working with Idunn's energy.
Milk: Milk can be used as an offering or as a symbol of nourishment and vitality.
Physicalities of Idunn

Idunn is often depicted as a young and beautiful woman. She is associated with spring and new growth, and is said to have long, flowing hair. She is often depicted wearing a simple, flowing dress or tunic, and may be shown carrying a basket of golden apples.

Symbols:

Apples: Apples are the most important symbol associated with Idunn, as she is the keeper of the golden apples of immortality.
Spring flowers: Spring flowers are a symbol of new growth and vitality, and are associated with Idunn's energy.
Baskets: Baskets are often depicted in images of Idunn, as she is said to carry a basket of golden apples.
Offering items:

Apples: Apples are the most fitting offering for Idunn, as she is the keeper of the golden apples.
Honey: Honey is associated with sweetness and Weapons and jewelry:

Idunn is not typically associated with weapons, as she is a goddess of youth and vitality rather than of battle. However, she may be depicted wearing simple jewelry such as bracelets or necklaces.

Hair and tattoos:

Idunn is said to have long, flowing hair, which is often depicted as blonde or light brown. There is no mention of tattoos associated with Idunn in Norse mythology.

Tarot card and constellation:

There is no specific tarot card or constellation associated with Idunn in Norse mythology.

Story of Idunn:

In Norse mythology, Idunn plays a key role in the preservation of the gods' youth and vitality. One day, the trickster god Loki came across Idunn while she was gathering golden apples. Loki convinced Idunn to accompany him outside of Asgard, the realm of the gods, under the pretense of gathering more apples.

Once outside of Asgard, Loki revealed his true intentions and abducted Idunn. The gods soon began to feel the effects of aging and weakness without the golden apples, and realized that Idunn was missing. They eventually found Loki and forced him to reveal Idunn's location.

Idunn was rescued and brought back to Asgard, where she was able to restore the gods' youth and vitality with the golden apples. This story highlights the importance of Idunn's role in Norse mythology, and the consequences that can occur when her power is not respected.