During my turn i activate branded fusion sending, albaz + nibiru to sum https://yugipedia.com/wiki/Titaniklad_the_Ash_Dragon, his atk is 2500+400+1100 = 4000atk,
During the battle phase i declare a attack againt a 2500 atk monster the opponent controls, on attack declaration my opponent activate (imperm/skill drain) to negate my monster effect, does my ash dragon atk drops to 2500?
Ash dragon condition effect: (Gains ATK equal to the combined original Levels of the monsters used for its Fusion Summon x 100.)
A similar ruling of the same archetype is fleur whoes attack wont drop cause the attack boost already have being applied,
does ash dragon behaves like fleur or the atk drops?