If I understand it right, with the friend system you'll be able to select a friend or somebody random (if you've got no friends registered) and use that friend's SB twice.
I'll quote those infos from a reddit post:
- You can only use each individual player once per day.
- The power of the SB scales by the equipped gear.
- RS applies! This counts for both gear and characters, if you're doing an FF6 dungeon, choosing an FF6 character for your friend summon will give you the RS for that character, even if the character perfoming the SB (i.e. your own character) is from a different realm.
- You can follow up to 100 players. Following a player increases the chance they appear in the list of 10 players, but you will still have some random players in the list.
- You will recieve 200 gil per time someone uses your character as a friend summon (received on daily login).
So is it twice the SB of a friend per dungeon, round, or day ?
I'll use the same terminology used by the game's data files:
World = one of the doors you click on from the main screen, or an event banner.
Example: FF6, Daily Dungeon, The Pulse Fal'cie, Legendary Plunderer
Dungeon = Once you're inside of a world, the next thing you click on
Example: Figaro Castle 1, Phoneix Cave (Elite), Sea of Elements: Heroic
Battle: An individual level inside of a dungeon. Entering a battle consumes stamina
Example: Sea of Elements: Heroic - Stage 1, Esper Cave - Depths
Round: The units that a battle is divided into. After you complete all the rounds of a battle, you get exp and get sent back to the battle list.
So, you can choose a friend to join you for a
dungeon. He will be present for all battles of the dungeon, and you can use his soul break at most twice during the entire dungeon.
