Megalian

 Megalian, or Heady as it is known as in Mega Man Battle Network 6, is a virus from the Mega Man Battle Network series. It has an aura around it that blocks attacks below a certain damage amount. Also, these auras have elemental properties, which thus have weaknesses to appropriate elements. The player must first destroy the aura, before damaging a stationary or moving Megalian, with an attack damage higher than the specified number on the aura. When this virus attacks, it shoots its head out of its aura towards its target, making them vulnerable to attacks. Stronger variants have stronger auras (of different elements) and their attacks extend over more panels.

Megalian/MegalianA/HeadyA
 Megalians are tan with red bands and have a blue aqua aura that protects them. Weak to elec.

Megalian2/MegalianH/HeadyH
 Megalian2 s are green with yellow bands and have a red heat aura that protects them. Weak to aqua.

Megalian3/MegalianW/HeadyW
 Megalian3 s are purple with gray bands and have a green wood aura that protects them. Weak to heat.

MegalianE
 MegalianEs are light-blue with green bands and have a yellow elec aura that protects them. Weak to wood.

HeadyE
 HeadyEs are gray with gray-blue bands. They are similar to MegalianEs.

RareHeady
 RareHeadys are blue with red-purple bands and have a yellow aura that protects them.

RareHeady2
 RareHeady2s are gold with light-blue bands and have a yellow aura that protects them.

Source
Sprite images found at Sprites INC