Mechanized Warfare

If a red or artifact source you control would deal damage to an opponent or a permanent an opponent controls, it deals that much damage plus 1 instead.

Magic Online Promos

First the automatons reinforced depleted squads. Then they replaced them entirely.

The Brothers' War Promos

The Brothers' War

If another effect modifies how much damage a source would deal to an opponent or a permanent they control, including preventing some of it, the player being dealt damage or the controller of the permanent being dealt damage chooses an order in which to apply those effects. If all of the damage is prevented, Mechanized Warfare's effect no longer applies.

If damage dealt by a red or artifact source you control is being divided or assigned among multiple opponents and/or permanents opponents' control, divide the original amount before adding 1. For example, if you cast a red spell that deals 4 damage divided among any number of targets and you choose to have it deal 2 damage to a creature and 2 damage to that creature's controller, that spell will deal 3 damage to each of them instead.

The additional 1 damage is dealt by the original source of damage. The additional damage isn't dealt by Mechanized Warfare.