Horde

Horde is a Boss Modifier that occurs only on Bosses, not on Champions. This modifier increases the number of minions that spawn with a boss, adding up to three to the support crew.

Horde Molten Fast was more than a Barbarian could manage.

The boss and minions are not altered in their stats at all; there are just more minions when the battle begins.

Horde:

• Monster Level Minimum: 31
• Available to: Bosses only.
• Damage Type: N/A.
• Additional Resistances: N/A.
• Can Not Spawn With: Avenger, Extra Health, Health Link, Illusionist, Missile Dampening, Invulnerable Minions, Shielding, Vampiric.

Note that the individual minions do not display "Horde" in their hover text, since the property only refers to the boss and doesn't affect the minion's behavior or stats in any way. Hence minions with this property might look like they are from a lower difficulty level, as they'll display fewer modifiers than expected.

Strategy

This really depends on the monster type and the other mods. More enemies is seldom a good thing, but attacks that hit multiple enemies are obviously useful.

Horde is most dangerous when the minions can create other Boss Modifiers, such as Frozen, Arcane Enchanted, Molten, and others along those lines, since more minions = more of those.

Horde is also nasty when the monsters hit very hard or otherwise support each other. One or two of the huge mallet smashing Cultist Berserkers isn't so hard, since they get stuck in the ground when they swing their huge clubs and miss. Five or six such enemies is very dangerous though, since while some are stuck others are just starting to swing.

Media

Horde is hard to tell in screenshots since it's just more of the minions, and the number of minions varies by monster type as well as difficulty level. It's most noticeable when the boss is a large creature. This is proved indirectly by the video below, which shows a battle with a Fallen Imp boss pack in Act 2. There are four Imp minions, which isn't much of an increase, considering it's Inferno.