Lucky Seven is none other than basicly a luck-based secret, when in a battle, if your HP reach 7777, the character that has the 7777 damage, will have their name flash, and then the character will then cause (regardless of level) 7777 damage to every single enemy the character will attack, regardless of stats of enemy, will be damaged 7777. Once your HP changes by any amount down or up, the effect is automatically ended.