The Shadow

The Shadow is an uncommon Droid that is mostly exclusive to The Darkness. They are only spawned naturally during the fight against The Dark One, where the boss will periodically spawn The Shadows along with other Darkness Droids. However, they can also be discovered outside of The Darkness, via a rare outcome from a Mystery Button. They seem to replace natural Anti and Friendly droid spawns in their corresponding worlds as of 1.5

Appearance
Similarly to other Darkness droids, The Shadow has the typical Droid helmet, but the droid itself is fully black.

Behavior
Whilst having the same attack pattern as most Droids (walk towards you), they have an insanely far sight range, high damage and are invincible. To make up for that, they are very slow, and do not need to be killed to clear the room, unless it had somehow been spawned "naturally" which is impossible as of currently.

While The Shadows summoned by The Dark One immediately die when their summoner is successfully vanquished (along with anything else it summons), any Shadows that weren't spawned by The Dark One outside of The Darkness (from a mystery button, for example), will follow the players until the next world, until it disappears with the message ‘The Shadow fades away..

Shadows summoned by The Dark One copy the players exact speed if you do not clear the room in time, this will end your run. (Not everything about this is fully known, something else could be causing this speed up.)

Trivia

 * The Shadow is naturally the slowest droid in-game. (Natural stats are their default stats, without any modifiers.)
 * Interestingly enough, The Shadow used to be able to get the Radioactive modifier from Reactor Droids, but this was patched in Beta 1.4.
 * During the fight with The Dark One, The Shadows spawned from The Dark One accelerates in speed (unknown if this has been changed).
 * There is only one way you can kill The Shadow, which would be getting the "piercing" modifier onto any droid that can hurt other droids (such as Anti Droids and Undead Droids) though this hasn't been confirmed. The only way to give such droids that modifier would be using the Necromancer class.
 * As of v1.5, using the item Crystal Torch, it is possible to remove the forcefield on The Shadow, which in turn allows you to kill them.
 * DJ is able to kill The Shadow using her second ability with the purple disc. (?)
 * The Burning and Shocking spells are also able to kill The Shadow as well.