change invocation

This spell can only be casted during the night.

The player makes a connection with his/her patreon. For doing so he concentrates on his patreon and constantly calls upon him. During the ritual the palyer consumes something that binds him with its patreon.

in the end, the patreon (DM) determines whether the player can change an invocation. The payer takes 1 lvl of exaustion because he didnt sleep.