Attunement level 1 grants you the following:

While holding this skull, you gain a +2 bonus to AC if you are wearing no armor and using no shield.

You can store 1 spell for use and cast it at will. Use this once per day

Improves intelligence by 1

Attunement level 2 grants you the following:

While holding this skull, you gain a +3 bonus to AC if you are wearing no armor and using no shield.

You can store 2 spels for use and cast them at will. Use this once per day

Improves intelligence by 2

Allows you to change up spells at will provided you have open spell slots

Attunement level 3 grants you the following:

While holding this skull, you gain a +5 bonus to AC if you are wearing no armor and using no shield.

You can store 5 spells for use and cast them at will. Use this once per day

Improves intelligence by 5

Allows you to change up spells at will provided you have open spell slots

Allows the caster to ignore material cost to all spells cast.

Notes: Bonus: Unarmored Armor Class, Bonus: Ability Score Maximum, Spell storage only allows the caster to store a spell that they can currently cast, at a level that is appropriate for the caster’s spellcasting ability. If you cannot cast the spell because it's not a known spell or its a higher level spell than you can cast you cannot store it. Additionally the spell that is to be stored cannot be stored at a higher level than the caster can cast. Example: a level 6 cannot store a level 20 nuke. Nor can a level 6 wizard store a first level spell as a 9th level (level 18-20) spell. The spell must be an appropriate spell for the caster and at a level the caster can cast. Some spells that are incompatible (aka broken af) such as power word kill, wish, knock, etc will not work with this item and which spells are determined by the DM. Ask DM before storing a spell in the item. Spell storage is intended to be stored until used. This item has one use and the use can be regained once per day. All terms of the item are subject to change at the DMs discretion., This item requires attunement. In addition to fully gain mastery of the item you must meditate while holding it. While looking into its eyes you can commune with the spirit of the departed. during long rest, Warding, Wristwear