For one green mana at sorcery speed, you can eliminate a threat as long as your creature survives the battle
After a quick look around the Internet, it appears Beacon of Unrest is used in just about every black EDH deck every created
"Dash [cost]" means "You may cast this card by paying [cost] rather than its mana cost," "If this spell's dash cost was paid, return the permanent this spell becomes to its owner's hand at the beginning of the next end step," and "As long as this permanent's dash cost was paid, it has haste." If you choose to pay the dash cost rather than the mana cost, you're still casting the spell
And the text comes in small, medium, or large, without any finer control
It is simply oozing convenience, value, efficiency and tempo
Added Grand Star