This event offers a quest to reward you for doing what you already want to do - be on the other side. A good benefit is that you can auto-play it, something very useful for a faction that wants to avoid hand clogging. You can just play it and wait to accomplish the quest. 
Generally at least one Seek The Horizon is easy to play as you will probably complete the quest once per game without much effort, the second copy however may need to be discarded for magic, maybe the first one you draw as you may need that magic to do something next turn. Remember that while the event is sitting there it is doing nothing for you, and sometimes you can’t afford that early game. 
While the event is definitely a powerful economic tool, if the cost of achieving it is “sacrificing” a unit in a suicidal mission, it may not be worth it, so don’t play a quest with the goal of sending a unit to die on the horizon with no other objective than completing this quest. Let it be a quest you complete pretty much doing what you already want to do, in the natural flow of playing the faction optimally.