Why does lowering an enemy stat multiply your damage in Dragonfire?

Because the enemy's defensive stat divides your damage of the matching type. Bring it down and every hit of that type, from your entire team, lands harder — off a single debuff.

The detail:

• −enemy Instinct → all your physical damage rises.
• −enemy Initiative → all your fire rises.
• −enemy Intelligence → all your tactical rises.

It's the most efficient lever in the deep game, because one debuffer amplifies the other two dragons' hits as well as its own. That's different from an offensive buff, which only helps one dragon.

It's also why you build a single damage type army: if everyone hits with fire, the −Initiative debuff your Jagadrix lands helps every attacker. If your team mixes physical, fire and tactical, each debuff only helps part of the army.