The Seeds of Destruction is the first side quest you are given in the Orient (Act III). When leaving the small encampment around the second Portal in the Babylon Outskirts (after leaving the Temple of Marduk), you see a farmer named Immeru running across the bridge, chased by Ichthians.
Talk to him and he will tell you of monsters attacking his farm. This farm is found just across the bridge. In the fields you will find lots of Coastal Ichthians with a white glow around them - kill them, then return to Immeru (who's still in the encampment) to get the reward.
The Ichthian attackers are usually fairly weak. However, being quest monsters, they often wear lots of magical and rare stuff and offer a good chance to acquire monster infrequents like the Ichthian Whomper.
Reward: 18000 experience