The Undead Tyrant - Act 1 Side Quest
Start Location: Herakleion
Quest Location: Tritons Ridge
Objective: Defeat Leucus 1 ~ Tyrant of Crete in the Ancient Tomb
The Undead Tyrant is the final side quest available to your in Greece and it is given to you by Diotimus in the town of Herakleion. For this quest you'll need to travel up to the northern portion of Triton's Ridge which is where you'll find the Ancient Tomb (shown on my map below). Inside of the Ancient Tomb you'll find Leucus I - Tyrant of Crete, a powerful undead enemy which you'll need to defeat.
Once you've defeated Leucus the quest will automatically complete, you will not have to return to town and turn it in. An upside to doing this quest is you'll find some Gorgons inside of the crypt Leucus is in which means you'll have a chance of getting the Stonebinder's Cuffs Monster Infrequent from them!