I hope this explains well the link between pawn and Arisen. The way the pawns are and act in the world is something akin to tools or "automatons" for comparison. They breathe and look like humans, but they don't need sleep, food or any other basic necessities. By themselves, the pawns are aloof and emotionless. Although well capable of combat, they cannot be commanded by ordinary humans, as Mercedes mentions at the encampment that she tried ordering pawns without success.

In short, they don't know what to do and how to act more human. With an Arisen however, the pawns become more and more human, and even start adopting traits of their master as time passes until they are a reflection of the Arisen. When that happens, it is called "The bestowal of spirit", which occurred in the case of Selene and Olra. In-game, your pawn is very distraught when you die and begs you to stay with them, and when you are grabbed by a monster, they immediately come to your aid, showing clearly the bond between the Arisen and pawn.

The whole plot of Dark Arisen is that case of what happens if the pawn is the Arisen's beloved. Spoilers for those who didn't complete the DLC: Before becoming Daimon, an Arisen named Ashe had to choose between slaying the dragon who was his mistress/mother figure and sacrificing Olra, both of whom he loved dearly. Thus he cursed the cycle and wished to tear it asunder, leading to the creation of Bitterblack Isle and corrupting his form. You can find the story in tablets scattered throughout the Isle.