Unhallowed robes
Unhallowed robes are a reward from the 2012 Hallowe'en event. The set consists of six pieces:
Unhallowed hood
Unhallowed torso
Unhallowed robe skirt
Unhallowed cloak
Unhallowed gloves
Unhallowed boots
Each piece can be bought for 25 ectoplasm from Brother Heinous, so the entire set costs 150 ectoplasm. Each ghost gives 10 ectoplasm and there are five per wave, so it would take a minimum of three complete waves to buy the entire robe set.
Any of the pieces can be changed to their Hallowed robes counterpart by joining Brother Righteous, or simply by clicking "switch colour" on the item (this can only be done when the item is unequipped). All owned items are changed at once.
A full set of Unhallowed or Hallowed robes is required before purchasing the ectoplasmator.