Conjuration

Three types of ‘conjuring’ exist in regard to the outer planes. Firstly is Summoning in which an extraplanar being is brought into the realm. Second is Calling in which an aspect of the being is summoned that can be talked to but not bound. Finally is the pact magic of a warlock that allows an extraplanar being to pull an aspect of their warlock into their realm in such a way as to make their own life viable to end.
In the first instance conjurers almost always produce Tieflings, Genasi or Aasimar due to the elementals being subjected to the laws of the material realm on entrance. Particularly powerful conjurers, such as those guided by a pact with a fiend, have been known to pull demons and devils through in their native forms but such summonings are extremely difficult and costly to succeed on. In addition any being pulled through such a means is unable to defend themselves against being bound. This means truly powerful planar beings never accept or fall victim to these summonings in fear that they may be bound to a mortal and denied their rightful power and place.
Calling is a weaker form of conjuring in which an extra-planar being is called on. The being has no requirement to appear and can delay accepting the Calling for centuries so long as the summoning circle remains in tact. When called a being appears as it does in its own plane and is able to interact with anything within the circle but its presence is a magical aspect and cannot be bound. Calling is often how demonic and celestial pacts are formed due to the willingness of powerful beings to appear when called if they believe they can gain from the exchange.
The third measure is arguably the most powerful. Somewhere between calling and summoning those subject to a pact with an extraplanar being can have their soul taken to the host plane to address their pact master. While the soul is in the other plane their physical form appears to be in a deathly sleep but remains breathing. These souls can be punished and harmed leading to comparable wounds appearing on their physical body. If killed they are also then subjected to the terms of their pact.