Regardless of how you use it, this card is good enough that almost every blue deck should play it
Number 187 Language English Legal Formats Commander, Legacy, Modern, Vintage Not Legal Formats Alchemy, Brawl, Competitive Brawl, Historic, Pauper, Pioneer, Standard, Timeless Rulings (6/7/2013) Although originally printed with a characteristic-defining ability that defined its color, this card now has a color indicator
If you are going the infinite combo routes available in a Chatterfang deck, Mirkwood Bats enables infinite burn damage to all of your opponents
Aether Syphon Aether Syphon is below average for drawing a card in blue, yet always a welcome effect
In the past it was sometimes considered rude and antagonistic to run narrow effects like Rest in Peace or Null Rod, since that one card could shut down one players entire deck