This is our unofficial guide for how to obtain all the Will Seeds from each Palace in Persona 5 Royal.
Collecting all three Will Seeds within each Palace will allow you to obtain exclusive accessories.
Once you have obtained the Crystal that is formed from the Will Seeds, you can equip it to a party member to grant them a skill. Later on, take it to Jose in Mementos to upgrade it to a Ring, which further increases the benefits of having it equipped to a party member.