Contracting

Is Pi a fan of Madoka? Yes. Yes they are.

Contracting refers to the act of a human and Pokemon agreeing to share their powers for whatever purposes they so choose. Both the noun and the verb are technically supposed to be capitalized, but no one's even doing that so y'know whatever. It involves magical processes that are not yet fully understood.

Poke ball
A Pokeball (of any type present in the games) is created at the moment of Contract. It can be seen as a symbol of the Contract itself; It is indestructible to everyone apart from the two parties involved in the Contract, but if either of them breaks it, the Contract will also end. Pokeball mechanics are largely the same as in the anime; they can shrink for storage, the Pokemon is vaguely aware of what is going on outside and can force themselves out.

If one's chosen Pokeball has a special animation on sending a Pokemon out, it can be incorporated into the transformation sequence.

Eligibility
Theoretically, any human and any Pokemon may form a Contract, but choosing the wrong partner makes things significantly more difficult.

Humans have varying levels of magical affinity; no one's sure how this is determined, although it might be related to genetics. Humans with higher magical affinity are able to hear Pokemon speech as legible speech instead of animal noises (a handful of in-between people can occasionally pick out staticky words and most of them end up devoted conspiracy theorists), and when contracted, can amplify the Pokemon's powers through transformation.

All Pokemon, including those with multiple souls or bodies, can Contract humans, and multiple humans entering into Contract with the same Pokemon has also occurred. However, no one has found a way to enter two Pokemon into the same Contract as of yet; this is likely due to the fact that the Contract mechanism revolves around the sharing of a single set of powers and multiple sets interfere with it somehow.

It is also possible for a non-human being to accept a Contract with a Pokemon, provided that they are intelligent enough to both understand and agree to the terms, but this has never happened and will not during the course of this RP.

Transformation
Each Contracted pair has one set of magical powers, taken from the Pokemon. As such, only one party is able to access these powers at a time. The Pokemon may use its own powers as long as it is not inside the Pokeball, but the human must transform to access them.

To transform, the human must be holding the Contract Pokeball with their partner inside. Transformation essentially shifts the Pokemon's powers to the human, replacing their clothing with a fancy costume and allowing them to access their partner's moves and ability. The contract Pokeball will always be present somewhere on this costume. Transforming may change the human's hair and eye colours as well, but it will never make them "part Pokemon" or grow any additional body parts. This transformation may be as fancy or as simple as one likes. Generally speaking, the transformed human will have to use their attacks in the same manner that their Pokemon would: for example, a human contracted with a Scolipede would have to physically spit poison in order to use Toxic, while one contracted with a Garbodor could shoot poison out of their arms to do the same. Some exceptions exist for cases in which the Pokemon has limbs not analogous to any human limbs, in which case another method may be substituted or a weapon be materialized as part of their costume for that purpose. While the transformation is in effect, the Pokemon is incomplete and physically can't leave the Pokeball.

The human can transform back at any point and will be forced out of their transformation if 1) their partner forcibly takes their powers back, 2) their Pokeball is removed from the Contract outfit, or 3) they're knocked out and can no longer battle.

Evolution
Pokemon who have met their evolution requirements can evolve while their partner is transformed, meaning most Pokemon (evolving through EXP gain) can evolve mid-battle. This will immediately and permanently update the human's costume and powers (as we are largely following the anime canon, you may change any amount of your character's moves on evolution as well). However, this has the potential to be extremely dangerous: the human has to deal with using a new set of powers while facing an enemy.

Mega Evolution
Mega evolution is also an option in this universe. It works as a temporary and highly draining "super mode"; it's extremely difficult for one to stay in a mega evolution for more than a few minutes, even for the most skilled of users. As in canon, it will require a Key Stone for the human and an appropriate mega stone for the Pokemon, as well as a strong bond between the two. There are exceptions within legendary Pokemon who can mega evolve with only their mega stone. Mega stones are fairly rare, but can sometimes be found after meteor showers as they are extraterrestrial in nature.

Mega evolution is essentially a shift in a Pokemon's powers, and will work accordingly. Both a Pokemon (outside its Pokeball) and a transformed human can mega evolve. In the human's case, it will trigger a second transformation, temporarily changing their costume to reflect their Pokemon's mega appearance. You may not change your character's moveset after a mega evolution but you may adjust their regular costume slightly to accommodate for the Key Stone.