Companions
Companions are NPCs that you have teamed up with. It is possible to to ask any NPC that you meet in the game to join you on your adventure.
It is possible to talk with any creature, even hostile, and convince them to join you. In which case they will become friendly.
Companions level up when you level up if they are on your team when defeating a boss. They also get an equal share of the loot from defeated NPCs.
While companions usually travel together, they may not always do so. Companions not close to each other can still communicate with each other. They can also teleport to one another.
Companions may accept to join you or leave you at their own will.