Every Forest , Island , Swamp , Mountain , and Plains has an intrinsic mana ability
Magic has been making shiny (foil) versions of their cards since 1998, and its been a core part of this games addictive appeal ever since
The Harbinger should, obviously, only be played in mono-blue Merfolk decks, and preferably in control shells that focus on icing out the opponent from doing much of anything rather than overwhelming them with tons of creatures, just like Richard Garfield intended
You can't do so later in combat, and creatures put onto the battlefield attacking can't be exerted
Expensive Upgrade: Solphim, Mayhem Dominus Sure, Valgavoth is more about life loss than damage specifically, but there are lots of damaging cards in this group slug deck, and Solphim, Mayhem Dominus is going to make them all work so much harder
What is more, overloading Vandalblast comes with no risk, since this card will not affect the caster's own artifacts