Aegis is a boss in Antiqua.
After stealing the Diamond Eyes from the Hero and returning to Nobilia, Horace's evil twin placed them in the eyes of the sacred dog statue in order to revive the power contained within. An explosion of energy soon emerged from the statue, destroying it and revealing Aegis within. The hero and his Dog destroyed Aegis, stopping the twin's plans.
With Aegis' destruction, it left behind a malfunctioning Energy Core on the verge of exploding. Tiny quickly appeared and threw the Energy Core as hard as he could, sending it all the way to Horace's Camp, where it exploded at the base of the waterfall, opening a passage into the Oglin Caves.
Aegis is only vulnerable when its face is exposed. It manifests various masks and is immune to damage when wearing one. Aegis does not fight itself, but summons other monsters to attack, depending on the current mask. When wearing the sun mask it summons Will o' the Wisps, when wearing the moon mask it summons Bad Dawgs, and when wearing the bull mask it summons Skullclaws. These monsters are nuisances and should be killed to avoid the player being overwhelmed, but the focus should be on striking Aegis whenever its mask falls.
Overall Aegis is not a difficult boss; it's minions are easily slain and it otherwise does nothing. The only difficulty is that the fight is long due to Aegis becoming immune to damage often and its high HP.
Defeating Aegis will reward the player with 3,000 experience and 1,200 jewels. Horace will also give the player the Staff of Life after the battle if they have six Call Beads; otherwise he gives them Call Beads until they have six.
The Aegis is an object carried by Zeus and Athena in the Iliad. It is historically ambiguous if the Aegis was an animal hide or a shield, or even both.