Chimaera (Warcraft III)

The mysterious Chimaera of Ashenvale Forest are deadly, territorial beasts who have developed an empathic bond with the Night Elf race. The fearsome, two-headed Chimaera fly above the dark forestlands spewing forth their terrible breath weapons upon all who would defy the sanctity of Kalimdor.

Information
Chimaeras are one of the ultimate Night Elf units. Like Frost Wyrms, Chimaeras deal massive damage against enemy ground units with an impressive area of effect, though they move rather slowly. Though unlike these undead dragons, the Chimaeras cannot damage enemy aerial units. Until Corrosive Breath is researched, Chimaeras use a short-ranged, magic attack against buildings. Upon completion of this research, the Chimaera gains a second attack that only targets buildings.

Chimaeras are feared if well protected, because a group of six or more can easily destroy any ground unit with ease, including ranged combatants. In the event, they are relegated to base destroyers, try to target Town Halls and immediately run away as soon as someone tries to teleport to defend. Chimaeras can also be used to sabotage the enemy by killing their workers.

Night Elf players generally build three or four Chimaera Roosts to speed up the production of the Chimaeras. Generally, if the player trains Chimaeras, they are also accompanied by Hippogryphs, and never any ground units. Chimaeras are notorious for killing allied units due to the high splash damage incurred from their AoE, compared to Frost Wyrms. Their high cost and requirement of additional protection mean the player needs to have one or two expansions to properly maintain a force of Chimaeras. It's also important to have your Heroes carry a Staff of Returning to make sure the Chimaeras don't die if they get focused on.

Being the only heavy air unit that is only limited to targeting ground enemies, any aerial unit easily counters a Chimaera. Some players may try to use Chimaeras to target town halls due to their longer range, so defensive towers will typically not work against them.
 * Counters

Spell-immune units like Dryads can also work due to their spell immunity protecting them from magic attacks. Alternatively, due to their slow speed, one could grab an ensnare unit (Raiders or Crypt Fiends) to snag the beasts before they get away, or use their own aerial units to pursue them.

Corrosive B reath (Passive)

 * Hurls a ball of corrosive bile that is effective against buildings.