Armored Formation

You bolster the defenses of those nearby. Choose up to twelve willing creatures in range. When an affected creature is within 5 feet of at least one other affected creature, they create a formation. The formation must be a contiguous grouping of affected creatures, and each affected creature must be within 5 feet of at least one other affected creature within the formation. If the formation ever has less than two affected creatures, it ends, and an affected creature that moves further than 5 feet from other creatures in formation is no longer in that formation. Affected creatures don't have to all be in the same formation, and they can create or end as many formations of various sizes as they want for the duration of the spell. Each creature in a formation gains a bonus depending on how many affected creatures are in that formation.
Two or More Creatures. Each creature gains a +2 bonus to AC.
Four or More Creatures. Each creature gains a +2 bonus to AC, and when it hits with any weapon, it deals an extra 1d6 damage of the weapon's type.
Six or More Creatures. Each creature gains a +3 bonus to AC, and when it hits with any weapon, it deals an extra 2d6 damage of the weapon's type.