It's on the stack when you choose its target
This allows you to use potentially powerful cards like Constant Mists and at least get a powerful creature to replace the land you lose
When it comes to pure value, however, I must say Mox Jasper tops my list
Dont forget to use this information draft your favorite cards (or players) in one of our Thousand Leagues public fantasy leagueswhere you could win a an uncut War of the Spark foil rare sheetor create your own league and invite your friends!
Given it's an instant, you can respond to a "titan" reshuffle graveyard trigger, and reanimate any of the odd mana cost Eldrazi if you want
For an example of what Topps 1951 cards looked like, take a look below: For that series only, it was framed to be more like a game (a trading card game, perhaps?) , and each players cards could affect the game, such as drawing a strike or a ball card would mean your pitcher threw a strike or a ball, etc