[Spell] Contact Creature: Speak the true name of an extraplanar creature. The creature makes a request or demand of you. Once you meet that request or demand, your soul is linked to that creature's soul.
[Spell] Summon Creature: Speak the true name of an extraplanar creature whose soul is linked to yours via Contact Creature, and give it a command. It appears at your side and follows that command until it is fulfilled, at which point it returns to its home.
[Action] You can spend a few hours studying or researching an extraplanar creature and make a roll to learn its true name.