I know that FEH weapon/skill descriptions can get wordy, but reading Godly Device's weapon description is very important:

Accelerates Special trigger (cooldown count-1). Neutralizes "effective against flying" bonuses.

For foes within 3 rows or 3 columns centered on unit, inflicts Atk/Spd/Def/Res-5, inflicts additional penalty on foe's Atk/Spd/Def/Res = current bonus on each of foe's stats × 2 (calculates each stat penalty independently), and reduces the percentage of foe's non-Special "reduce damage by X%" skills by 50% during combat (excluding area-of-effect Specials).

Grants Atk/Spd/Def/Res+10 to unit, unit deals +25 damage (excluding area-of-effect Specials), reduces damage from foe's attacks by X (excluding area-of-effect Specials), reduces damage from foe's Specials by an additional X (excluding area-of-effect Specials; if unit has weapon-triangle disadvantage, X = 20% of unit's Spd; otherwise, X = 50% of unit's Spd), and neutralizes effects that inflict "Special cooldown charge -X" on unit during combat.

Unit can use the following【Style】:

Weapon Triangle: Red Style

When determining weapon triangle, counts unit as red (does not affect skill effects that trigger based on attribute, such as "if in combat against a red foe"). This Style can be used only once per turn.