Each party member who wishes to receive credit for the fight needs at least one of the Key Items. However, the Custom Cardians' number and resistances are determined by the Key Items of the player who initiates the fight has collected.
Even if other members in the party have collected a Key Item, if the player who initiates the fight does not have it, the Custom Cardians will be immune to that damage type.
There is a ??? located on an Ancient Magical Gizmo directly opposite the entrance, examining it will give you the option to start the fight. Be warned that Confrontation status causes pets to DESPAWN when you activate the battle.
The number of Cardians is dependent upon the number of Key Items the player who initiates the battle has collected. By default, there are 20, and for each additional orb, the number of Cardians is reduced by 5 for a minimum of 5 with all 4 orbs collected.
As noted above, the player who initiates the battle sets the Cardians' resistances for the rest of the party, regardless of which orbs other party members have collected.
Enfeebling magic effects, including all forms of Sleep, still function as usual even if the player has not received the Orb of Coins. The initial damage from Damage Over Time spells does not process, but the damage-per-tick does.
The Professor consents to lend you her aid, but as expected, there's a price to be paid. Within a Cardian in the Outer Horutoto Ruins lies the reagent she does seek; return it to her, that you might avert a fate most bleak!
SPOILER WARNING: Click here for additional details about this story line.