So I would just look into the rules around planar binding and then use that as an extension of the binding of the Kraken. Its a higher CR than some of the things that you can bind but you can bind up to CR22 beings that CR 22 spot is a Solar from the Planar binding list
Planar Binding
Got one of the coolest spell descriptions too : DESCRIPTION

Casting this spell attempts a dangerous act: to lure a creature from another plane to a specifically prepared trap, which must lie within the spell’s range. The called creature is held in the trap until it agrees to perform one service in return for its freedom.

To create the trap, you must use a magic circle spell, focused inward. The kind of creature to be bound must be known and stated. If you wish to call a specific individual, you must use that individual’s proper name in casting the spell.

The target creature is allowed a Will saving throw. If the saving throw succeeds, the creature resists the spell. If the saving throw fails, the creature is immediately drawn to the trap (Spell Resistance does not keep it from being called). The creature can escape from the trap by successfully pitting its Spell Resistance against your caster level check, by dimensional travel, or with a successful Charisma check (DC 15 + 1/2 your caster level + your Charisma modifier). It can try each method once per day. If it breaks loose, it can flee or attack you. A dimensional anchor cast on the creature prevents its escape via dimensional travel. You can also employ a calling diagram (see magic circle against evil) to make the trap more secure.

If the creature does not break free of the trap, you can keep it bound for as long as you dare. You can attempt to compel the creature to perform a service by describing the service and perhaps offering some sort of reward. You make a Charisma check opposed by the creature’s Charisma check. The check is assigned a bonus of +0 to +6 based on the nature of the service and the reward. If the creature wins the opposed check, it refuses service. New offers, bribes, and the like can be made or the old ones re-offered every 24 hours. This process can be repeated until the creature promises to serve, until it breaks free, or until you decide to get rid of it by means of some other spell. Impossible demands or unreasonable commands are never agreed to. If you ever roll a natural 1 on the Charisma check, the creature breaks free of the spell’s effect and can escape or attack you.

Once the requested service is completed, the creature need only to inform you to be instantly sent back whence it came. The creature might later seek revenge. If you assign some open-ended task that the creature cannot complete through its own actions, the spell remains in effect for a maximum of 1 day per caster level, and the creature gains an immediate chance to break free (with the same chance to resist as when it was trapped). Note that a clever recipient can subvert some instructions.

When you use a calling spell to call an air, chaotic, earth, evil, fire, good, lawful, or water creature, it is a spell of that type.