"At first, when you pick up the abandoned sack you think it's filled with gold, but when you open it you find a perfectly good suit of Chain Mail instead."
The Chain Mail is one of the most rudimentary armors found in the game. It protects more than the Leather but less than the Plate Mail. It works as a nice substitute for Combat in the beginning, but sadly the armor comes with some unpleasant side-effects that will disturb might and magic heroes alike.
The movement penalty is not particularly annoying for magic heroes, but it is for might heroes, even if they posses a ranged attack. The mana cost increase matters for magic heroes, since this item is only used in the first few weeks and heroes have little mana then.
The Chain Mail does it's duty in the beginning, but it should be replaced by a better armor as soon as possible.