This price will fall quite far, and you should absolutely sell any copies you open/trade for at the prerelease before it drops to $20
Ultimecia, Temporal Threat and Lightning, Security Sergeant are the cheapest two, worth about $1.20 and $1.40, respectively
How youre going to use Doomsday varies with the format (Cube, Vintage, EDH), but youll usually want a card like Laboratory Maniac or Thassa's Oracle and draw spells like Gush or Gitaxian Probe
This time, it relies a lot less on opposing graveyards to the order it only cares about your own
Each has numbering over the normal 204, which is normally reserved for Enchanted cards
If you do, each opponent loses life and you gain life equal to the total amount lost that way