The Dreadhorde engages all enemy forces in the Region in battle; they automatically Reinforce one another. It takes a -20% Combat Strength Multiplier for this engagement.
After that combat resolves, the Dreadhorde deals 0.5% of its Effective Combat Strength in damage to the Security of the Region it is located in.
If the Security is reduced to zero in this way, the remainder of the damage is dealt to the Economy of the Region.