Parties are a core gameplay mechanic in Granblue Fantasy. A party consists of 1 to 6 characters, a set of 0 to 10 weapons and a set of 1 to 5 summons.
Each party uses 3 main members and 2 sub members. In a quest, your main character and your 3 main members will immediately enter battle, based on the order that they are present in character slots. Only 4 members may be in battle at a time.
Each party uses 1 main weapon and up to 9 sub weapons. This is colloquially known as the "weapon grid", or "grid" for short. The main weapon of the grid dictates the element and charge attack of your main character. Each weapon can have up to two modifiers known as Weapon Skills. All weapons in your grid are always active (unless participating in a Skill-bound battle) and will apply to all applicable characters in your party. The HP and ATK values of all equipped weapons apply directly to all characters in your party. If you do not have a main weapon equipped, your main weapon will automatically become an extremely weak class-specific weapon in battle.
Each party uses 1 main summon and up to 4 sub summons. This is also known as the "summon grid". Aura effects from summons only apply when used as a main summon or support summon. The HP and ATK values of all equipped summons (excluding support summons) apply directly to all characters in your party.