Geru

 (also known as Geeru or Gale) are lizard-like warriors who appeared in The Adventure of Link. They are very similar in appearance to Lizalfos. They fight primarily using maces, and defend themselves with a shield. They are the strongest enemies Link will face outside of the Dungeons in the game, and are similar in battle to Iron Knuckles.

Geru seem highly organised and most of them are found in the valleys of East Hyrule where they attack from beyond high walls, and many also inhabit the Valley of Death before the Great Palace. They do not appear in the Palaces, so it is likely that they are followers of Ganon.

Variations
Geru appear in orange, red, and blue forms, each with slightly different behavior. Both Red and Blue Geru are armed with maces (which cannot be repelled with Link's shield, rather a Reflect Spell), however the blue form also has the ability to throw its weapon, making it one of the strongest and most dangerous enemies in the game. The orange ones carry spears that can be blocked with Link's shield and can attack high and low, just like an Iron Knuckle. All Geru are skilled with a shield, making damaging them very challenging. While its possible to keep a Red Geru from getting close enough to hit with its mace, the Blue Geru can keep defending while causing a large amount of damage by throwing maces, so the Reflect magic is recommended if you intend to fight one.

Some Red Geru also appear from atop walls and hurl boulders at Link. These Geru cannot be attacked by normal means, and can only be destroyed with the Thunder magic.

Red and Orange Geru are commonly found in caves and forest areas of southern East Hyrule. Blue ones, however, are seen inhabiting darker grounds such as the graveyard and the Valley of Death.

Trivia

 * Geru seem to be based on a Japanese tree lizard.