Golem

Golems (ゴーレム, Gōremu), coming in many shapes and sizes, are an item unique to the D.Gray-man universe and used by the Black Order and the Noah Family alike.

Purpose
Golems are seen used, specifically by the Black Order, as communication devices, able to be hooked up to phone-like devices that Finders carry in large packs on their backs or even to regular telephones for the purpose of contacting the Order or other golems, though contact from golem to golem does not seem to require the phone line hookup.

Some golems, such as Timcanpy and Lero, are presumably even made in different ways, and are shown to have more abilities than others. For instance, Lero is often seen being used as a method of transportation by Road Kamelot, a feat presumed impossible for other golems (Timcanpy included).

Design
Order-issue golems are uniformly black and mechanized, with a spherical shape being the standard form, though they have also been seen in diamond shapes (such as Lenalee Lee's golem ), and in raindrop shapes (such as Lavi's golem ), and these personalized golems tend to be seen with their owners at most times.

Exploration
There also seem to be a large amount of golems that are stationed outside of the European Branch who act as moving security cameras, monitoring those who come into and out of the Order.

Order-issue golems also seem to be personalized and imprinted to a specific user, as Komui Lee mentions after the mass murders of field personnel Exorcists and Finders that the golem responsible for contacting the Order in that case was traced back to Suman Dark and could only be used by him because personalized golems are voice activated.

Mechanized golems are incapable of passing though the Ark, as it is noted when Allen uses it to travel from Asia Branch to Edo that Bak Chang had to create a special earpiece for Allen to communicate with Komui Lee in the European Branch because the communicator golems were destroyed upon trying to enter the Ark door.

Custom-made golems
There also appear to be organic-based golems, such as Timcanpy and Lero, who were likely created by use of magic, as it is noted that Cross Marian, who owned Timcanpy before Allen, is versed in magic. It is also seen that, when Nea Walker was awakened within Allen, Timcanpy is either capable of casting spells or has several pre-cast spells stored within him.

Trivia

 * Though most golems are mechanized (specifically, the Order-issue golems), there are those that seem to be organic, such as Timcanpy, Lero and Tyki Mikk's Teez.
 * Tyki Mikk's Teez are the only known golems known to eat flesh.
 * Golems are figures of the Jewish folklore or Jewish bibles.