Mystic Ally

Mystic Ally is a Focus Monk skill in Diablo III, unlocked at level 22.

In-game
Passively summons a permanent companion: the spiritual copy of the Monk. It follows the Monk around, attacking enemies with the same attack speed as the Monk, dealing 130% damage as Physical per hit. It cannot use any of the Monk's skills. The Ally can be killed (has the same Toughness as the Monk), but is automatically revived in 5 seconds.

When activated, increases damage done by the Ally's attacks by +50% (to 195% damage as Physical).

Runes

 * Water Ally: damage type changes to Cold, and attacks Chill enemies for 2 seconds, slowing them by 60%. When activated, instead of damage buff, the Ally transforms into crushing wave for up to 15 seconds, dealing up to 7 attacks for 625% damage as Cold each. Enemies hit by the wave are Frozen for 3 seconds.
 * Fire Ally: damage type changes to Fire, the Ally's attack becomes a piercing short burst (so it hits all enemies in an 18-yard line, similar to Deadly Reach), and also increases the Monk's damage by 10% (not multiplicative to similar modifiers). When activated, instead of the Ally's damage buff, the Ally turns into 5 smaller Allies, each exploding for 480% damage as Fire. Once all of them detonate, or after 15 seconds, the Ally's normal form returns.
 * Air Ally: the Ally also deals 45% damage as Physical per tick to enemies within 10 yards of it (similar to Sweeping Wind), and increases the Monk's Spirit regeneration by +4 per second. When activated, instead of damage buff, restores 100 Spirit to the Monk.
 * Enduring Ally: also increases the Monk's Life regeneration (the amount scales with level, up to 10728 at level 70, and is further increased by 7% of the Monk's own Life regeneration). When activated, instead of damage buff, sacrifices the Ally and heals the Monk to 100% of maximum Life. The cooldown increases to 50 seconds.
 * Earth Ally: also increases the Monk's maximum Life by 20%. When activated, instead of damage buff, turns the Ally into the rolling boulder for 8 seconds. The boulder rolls over enemies, dealing 380% damage as Physical per tick and knocking them up for 1 second.

Non-rune enhancements

 * The Crudest Boots (Legendary Boots): summons double the amount of Mystic Allies at once. Both passive bonuses and their activated attacks are duplicated.
 * Bindings of the Lesser Gods (Legendary Bracers): enemies hit by Cyclone Strike will take 150-200% more damage from Mystic Allies for 5 seconds, not stacking.
 * Inna's Reach (Set Daibo): increases damage of Mystic Ally by 90-120%.
 * Inna's Mantra Set (Set Bonus for 2 items): increases passive effects of Mystic Ally by +100%.
 * Inna's Mantra Set (Set Bonus for 6 items): summons five Mystic Allies (one for each skill rune), even if the skill is not taken. For every Mystic Ally, Monk's damage increases by 950%.
 * Tasker and Theo (Legendary Gloves): increases Attack Speed by 40-50%.
 * Enforcer (Legendary Gem): increases damage by 15% (+0.3% per rank) and reduces damage taken by 90% (rank 25 bonus).