An Arcane Coffer are bonus chests found at the end of each Dread Ring Campaign lair. Arcane Coffers are the only source of the 
[Eye of Lathander].
They can be looted using a 
[Silver Gauntlet], 
[Platinum Gauntlet], 
[Mithral Gauntlet], 
[Adamantine Gauntlet] or 
[Star Metal Gauntlet].