Quote from genini1Each copy is a separate object and all their bonuses are cumulative. So if you had 2 Door of Destinies out and cast a Myr then each one would get a counter and the Myr would get +1/+1 from each Door.
Quote from HungLowHoboSo basically what it is brought down to, is their is no way to stop an activated ability like this without a cancel or something else that specifically stops an activated ability correct? Whether it's paying mana for the ability, or tapping it to active the ability, it will still resolve?
112.7a Once activated or triggered, an ability exists on the stack independently of its source. Destruction or removal of the source after that time won't affect the ability.
2.4 Conceding or Intentionally Drawing Games or Matches
If a game or match is not completed, players may concede or mutually agree to a draw in that game or match. A
match is considered complete once the result slip is filled out or, if match slips are not being used, a player leaves
the table after game play is finished. Until that point, either player may concede to or draw with the other, though
if the conceding player won a game in the match, the match must be reported as 2-1. Intentional draws are always
reported as 0-0-3.
Players may not agree to a concession or draw in exchange for any reward or incentive. Doing so will be
considered Bribery (see section 5.2).
If a player refuses to play, it is assumed that he or she has conceded the match.