There is no limit to the number of characters who can be in a party. Characters can only be in one party at a time and will be removed from the party if they change characters or log out.
A party can be created by opening the online player list with
O, then right-clicking on a player and selecting
invite to party.
The other player will receive a popup showing them who invited them to the party and allowing them accept or decline the invite.
Any player in the party can invite other characters to join the party.
Players who are already in a party cannot be invited to join a different party.
A player can leave the party by right-clicking any character in the party list and selecting
The character that creates the party by sending the first invite is the party owner. If the party owner leaves, the first player who was invited to the party becomes the new party owner.
The party owner can remove players from the party by right-clicking them in the party list and
remove from party.
XP and loot are shared for all enemy kills, regardless of the party membership of the player and the character who deals the killing damage to the enemy. Party members still need to enter combat with an enemy in order to get rewards, by dealing damage to the enemy or healing another character that is in combat with the enemy. Just being in the party with the killing player isn't enough. Dying during combat removes a character's reward participation until they enter combat again.
XP for each party member is calculated as if they had killed the monster individually (level differences are calculated separately for rewarding XP).
Party Members List
If a player is in a party, a list of other members of the party will be displayed under their HUD in the top left of the screen. The party member list displays each other player's name, level, health, and mana. The box of each party member will be highlighted differently if they are in a different zone, in the same zone, or nearby (visible) to the player.
The style of the party members list can be changed in the options menu. The available styles are Full, Compact (smaller), and Minimal (hides mana).