Vez'nan

He enters the fight as three Vez'nans, and two of them are illusions. The first two brought to 0 health are the illusions, whichever ones they are.

An illusion brought to 0 health bursts: soldiers, heroes and enemies within a radius of 200 are killed outright (bosses and summons that cannot be killed outright are spared), and a Demon Lord appears in its place.

Every 15 seconds an illusion locks 2 towers within a radius of 300 for up to 10 seconds. Tapping a locked tower 3 times frees it. The real Vez'nan does not lock towers.

When the second illusion falls, the last Vez'nan becomes the real one: he teleports to the middle of the battlefield, every other enemy dies, and the last wave starts.

As he appears, soldiers are killed outright (summons that cannot be killed outright are spared), heroes are stunned for 14 seconds, and he heals to his full 5,999 / 6,999 / 7,999 / 9,999 (Casual / Normal / Veteran / Impossible) health.

Every 5 seconds he fires a demonic bolt at a unit, dealing 180-240 true damage.

Every 7 seconds the real Vez'nan drains up to 5 units within a radius of 250: each takes 550-750 true damage (a soldier that damage would kill is consumed instead), and he heals 100 health per unit drained.

When he dies, every enemy still on the battlefield dies with him.