If Double Lion's user performs a follow-up attack, either by a speed check or a skill such as Brash Assault 3, users will land a total of 4 attacks during combat.
A foe with skills such as Null Follow-Up 3 will neutralize any of Double Lion's user's skills that guarantee follow-up attacks.
If unit initiates combat means if the user starts a combat on their turn. The unit does not need to deal damage, nor be the first to attack.
However, if the effect is applied after combat, the unit must also survive it to fulfill this condition.
Hardy Bearing 3 do not affect the extra attack.
Brash Assault 3, users will land a total of 4 attacks during combat.
Null Follow-Up 3 will neutralize any of Double Lion's user's skills that guarantee follow-up attacks.
Embla's Ward or 
Múspellflame will neutralize all sources of out of combat damage except Røkkr area-of-effect Specials.
Røkkr will neutralize all sources of out of combat damage except area-of-effect Specials.
Mystic Boost 3.
Fury 1 + 
Mystic Boost 2 = +2 HP, and 
Fury 3 + 
Royal Sword, which in extension was exclusive to Alm, though here it can be used by 
Celica: Warrior Priestess, and with any weapon she equips. In Fire Emblem Gaiden, Celica was able to wield the 
Double Lion didn't exist at the time, thus Celica with Double Lion is an impossibility on two fronts.
