Introduction: Familiar contracts are contracts made between entities of the main plane and entities of a lesser plane. While summoning contracts are more like temporary mercenary contracts, familiar contracts are soul-binding and more permanent. It is like binding an entity to you like you would bind a skill.

Notes:

1. The familiar bonded to the summoner is loyal to the summoner. Trying to harm the summoner, directly or indirectly, will result in backlash. Depending on the grade of the contract, the familiar would receive varying degrees of soul damage upon the death of its summoner's soul. Hence, it would usually fight to the death to defend its summoner.
2. It is pseudo immortal. While it can die, the death is only temporary. After a 30 day cooldown, it can be revived... for a heavy price of 100 times its base worth. While it is dead, the familiar will lay dormant in the user's inner realm. If the summoner's soul perishes while it is dead, it would be revived in its own plane... With varying degrees of soul damage. Possibly dying outright.
3. Since a familiar needs to connect to the summoner's soul itself, it requires a unique skill slot from both parties.
4. While the familiar isn't dead, a summoner may be able to use several skills from the familiar and vice versa. Switching a skill requires to unequip all the current skills and wait for 48 hours. The number of skills is determined by the grade of the contract.
5. The contract grade is initially G. However, through mutual understanding, bonding,  attuning to each other's soul wavelengths, and growing stronger together, the connection can deepen, tethering the souls together. The maximum grade is EX. Raising the grade is hard, and the higher the grade, the harder it is to raise.
6. The number of skills that could be shared is between 0 to 4 and can be obtained on grades F, C, S, and EX. If a skill that is borrowed is of a higher grade than the contract grade, it would be reduced to the grade of the contract. The LVL would be like that of the original.
7. A summoner may be able to use the attunements of a familiar and vice versa. The higher the contract grade, the better the grade of the attunement that can be borrowed. Cannot surpass the original attunement grade.
8. A user can only bind a single familiar at a time. The higher the familiar contract grade, the harder it is to unbind later, and the bigger the backlash when unbinding. At the maximum grade, the souls can be considered intertwined.
9. A user may be able to un-summon and summon the familiar at will as long as it is in the user's immediate proximity.
10. Killing a familiar doesn't give points to the one that killed it.
11. A familiar has a mind of its own. It may think and act on its own if not commanded otherwise. Sometimes, it might even do things that the user might not wish... Such as attacking entities its master does not wish to attack, buying useless trinkets, falling in love... That is why a summoner should give strict orders from the get-go.
12. While it is loyal to the summoner, there is a limit. If the summoner abuses the familiar, or there is a major disagreement, then it will lack motivation when obeying orders. It might even try and fight suicidally. Even if an absolute command is given, the familiar's movements will turn rigid and mechanical. If the contract grade is low enough, it will even take the initiative to break the contract.
13. If somehow the familiar's soul is destroyed, the user will suffer a backlash. Such a backlash can injure the soul, possibly cripple it, or outright kill the user. The amount of damage is determined by the contract grade.
14. If the user dies, but the soul is still intact and preserved, the familiar can still live on. If the contract grade is high enough, it will usually seek to somehow revive or reincarnate its master, if possible.
15. A familiar may only be less than or equal in level to its summoner.
16. To summon a familiar, a connection is needed to a god of a lesser plane. To form that connection, an offering must be made. Usually in the form of items of high worth... Or souls. Points are not a valid offering, as they have no use for them. After the familiar contract is established, the connection to the god can, and usually will be cut off.
17. All points the familiar gets from kills go to the master. The master can distribute points back to the familiar.
18. A familiar can only grow through the points it is given and not through other resources.
19. Familiar contracts can become permanent, even in godhood. That, as well as the fact that it is expensive, usually makes others think thrice before performing it. Only about one in every 1,000 humanoids possesses a familiar.
20. Summoning a familiar cost 100 times its base worth. However, because the familiar is usually much weaker than the summoner, the price is negligible.
21. A familiar may be reverse summoned to its lesser plane to gather resources and points. However, it also risks death by doing so. When the contract grade reaches grade S, the summoner may reverse summon itself into the familiars plane.
22. A familiars lifespan is determined by the lifespan of the summoner. If the contract is somehow broken, or the summoner's body is destroyed yet the soul is still intact, then the familiar's lifespan continues to tick away from when it stopped.
23. A familiar and summoner share a telepathic link and can understand each other's language and emotion. Not to be confused with feeling it. Just sensing it. The higher the contract grade, the deeper the sensing. Gradually, ever so slowly, the contract may affect the personality of both sides.