You add Geas to your grimoire for free. When you cast the spell using this feature, you can modify its casting to draft a binding contract. Instead of giving a verbal command, you write a legal contract that can contain up to 10 commands and conditions. You can include clauses that end the spell early or extend its duration to a maximum of 90 days. Instead of targeting a creature that you can see within range, the spell targets any creature that signs the contract within the duration.
A creature that willingly signs the contract as a Utilize action automatically fails its saving throw against the spell, whether or not the creature understands the nature of the contract.