A epic treasure map is an item in Evony TKR (The King's Return). It can be found after killing certain monsters or bosses, with some of them listed below.
The description of Epic Treasure Map in Evony TKR says:
Use it to locate a Lv5 Relic to search for Treasures.
Epic Treasure Map is known to drop from a number of bosses or monsters upon killing, including Griffin, Ifrit, Kamaitachi and Junior Cerberus.
Note: This list may be incomplete.