Here is the full list of all 11 Serment - there are Contract with a Devil achievements.
Get through the first payment.
Complete the contract.
Fully explore a dungeon floor.
Fully explore the dungeon.
Defeat an unweakened final boss.
Defeat Sera at full power.
Purchase every item in the weekend sales.
Have 100,000 G.
Reach level 50 with the main character.
Know your priorities ;)
Complete the battle gauntlet.