Aegislash has the ability to change forms during battle, depending on the moves it is using.
Aegislash's body resembles a golden sword with the blade pointing downwards. The edge of the blade is white and somewhat serrated near the tip. Its single eye, which is purple with a white, linear pupil, sits where the blade meets the hilt, where it is surrounded by black coloration. The handle is thick at its base, tapers as it progresses to the end, and is striated. Two cloth-like arms emerge from the sides of the hilt. Each arm is primarily black and ends in lavender, transitioned by a slight whorl between the two colors. It carries an ornate shield in at least one of its arms, usually the left arm.
Aegislash is capable of changing its stance in the middle of battle, depending on what moves it uses. It carries out offensive moves in its Blade Forme, in which it carries its shield in its left arm and exposes its blade, which it uses to slash its opponents. Defensive moves are performed in its Shield Forme, in which it holds its shield up in front of its blade, with both of its arms crossed behind the shield.
It is said to be able to detect the innate qualities of leadership; legend has it that whoever Aegislash recognizes as a worthy leader is destined to become king. Indeed, this Pokémon has attended and served generations of kings. It is also known to use its spectral power to manipulate people and Pokémon alike. Aegislash is the only known Pokémon that can learn King's Shield.
Aegislash appears to be based on a possessed sword and shield. Its disposition to sense an owner's potential as leaders and kings, seems to draw inspiration from the ideas of mythical swords of European legend, chiefly Excalibur.
Aegislash is a combination of Aegis (Zeus's shield in Greek mythology) and slash.
Gillgard may be a combination of Gilgamesh or gild (to cover with a layer of gold), 斬る kiru (to slay with a blade) or kill, and guard.