The typical multiplayer mechanics seen in the Souls series have been changed quite a bit in Elden Ring, and co-op now comes with the risk of getting invaded by other players. To accommodate these changes and make it possible for players to receive help during the most intense battles in the game, Elden Ring allows players to summon a variety of spirits to their aid.
Before it becomes possible to summon spirits, you will need to get your hands on the Spirit Calling Bell. This special item can be obtained as a gift from Renna the Witch, which players can meet in the Church of Elleh after your first visit, or by purchasing it from the Twin Maiden Husks in the Roundtable Hold. With this item, you will be able to summon the spirits dwelling from Spirit Ashes in your possession, ranging from spirits of regular common enemies like wolves and soldiers to more unique spirits. Each spirit type has a different FP cost, and the stronger the spirit, the higher the cost will be.
As spirits are meant to aid players during the most challenging combat encounters, they cannot be summoned anywhere, but only if a Rebirth Monument is present in an area. You can know if spirit summoning is possible at any given time when a tombstone icon is present in the left part of the screen. Summoned spirits also behave as if they were another character, so they can be affected by area of effects supportive spells and weapon arts.
All Spirit Ashes can also be upgraded the same way weapons can. To do so, you will need to complete Roderika's quest and interact with her in the Roundtable Hold. You will need Grave Gloveworts to improve Spirit Ashes, and you can find these items mostly in catacombs all over the Lands Between. Catacombs are also where you can find most Spirit Ashes, so make sure to explore each area to the fullest to expand your spirit summoning capabilities.