Cloak is a Basic item purchasable from the Arcane section of the Home Shop and from the Side Shop. It provides the holder with increased resistance to magic damage and is a component of Hood of Defiance and Glimmer Cape.
Below is a table of resists with various combinations:
Cloak is usually purchased in the process of building towards other items, especially Glimmer Cape.
Additionally heroes that have that have item slot space and that have enough HP to make use of the increased effective HP Cloak gives can obtain Cloak to increase their durability, examples in particular Lone Druid, Alchemist, and Dragon Knight. This can be a very cost efficient stand-alone item on any hero against teams with heavy spell damage for an item that costs slightly more gold than a Bracer. Notably on Centaur Cloak is often bought early to reduce self-damage from Double Edge.