Evil Chip (Battle Chip)

Evil Chips (あんこくチップ), and the similar Dark Chips (やみのチップ), are Battle Chips in the Mega Man Battle Network series that can only be used under dark conditions.

Mega Man Battle Network 3
Dark Chips are Giga Chips that require a Dark Hole panel open in the field to be used, which is created with the Hole Battle Chip.

Mega Man Battle Network 4
Evil Chips can only be used by MegaMan.EXE when his spirit has been significantly put under control of his Dark Soul. To open the entrance to Black Earth, the player must have the following 5 Evil Chips: Muramasa, Anubis, ElemDark, BlakWing, and BugCharg/BugCurse.

These chips do not turn a NetNavi evil, but like the DS version of Navi Chips they can only be used by Dark Navis.

All Evil Chips are present in Rockman.EXE 4.5 Real Operation, but they are no longer considered Evil Chips, the user being free to use them without these requirements.

DS Navi Chips
When a DS Navi is defeated (or when achieving the specific busting level against an SP Navi), MegaMan will receive that Navi's DS Chip. DS chips, like Evil Chips, can only be used by dark soul NetNavis. The power of these DS Navi chips also depends on the total number of open Dark Holes on the field on either player's side. Depending on the Navi Chip, this is a bonus of either +5 or +10 ATK for each Dark Hole on the field, with the bonus capping at 10 Dark Holes.

In Mega Man Battle Network 5, MegaMan cannot use these chips if he is not in Dark Mode (gained by using Dark Chips before), but other Navis (only in Liberation Missions) can use them.

Trivia

 * The BlackWing chip's attack animation is a direct copy of the attack animation of the DarkMan chips in Mega Man Battle Network 3.