Armour Bug

An Armour Bug is a Small symbiotic mechanical insect that will latch to a nearby creature and create a heavy chain link armour around the host. The Armour Bug attaches to the host through small spikes along the spine.

The Armour Bug creates two large insect legs that wrap around the hosts chest. These legs can detach from the body and reach out to attack enemies passing by. The armour bestows the Sentinel feat to the host and an additional Reaction for making Opportunity Attacks.

The Armour Bug is completely aware of the surroundings of the host and knows what the host knows or has known in the past. When the host is approached with a question that they have encountered the answer of before, the Armour Bug will telepathically communicate the answer them. The host automatically succeeds on any History checks.

If the host is a Monk or Barbarian, they lose no benefits from Unarmored Defence as the Armour Bug moulds to the host's body so well that they do not inhibit them in any way. 

Curse. The host cannot remove their attunement to the Armour Bug unless it is willing to. It is determined by the DM as to whether the Armour Bug would be willing to remove itself (e.g. another creature is available for the Armour Bug to attach to, the host is about to die or will be in a situation in which the Armour Bug will be destroyed). When the Armour Bug is willing to be removed, it will allow its spikes to retract from the creature

This armor consists of a coat and leggings (and perhaps a separate skirt) of leather covered with overlapping pieces of metal, much like the scales of a fish. The suit includes gauntlets.

Notes: Once the creature attunes to the Armour Bug, tiny spikes stab into the creatures back along their spine. These spikes aren't removed until they are willing retracted by the Armour Bug, Stealth Disadvantage