2010-06-15 If an activated ability of a creature you control costs no generic mana to activate (for example, if it costs , it costs , or it costs only nonmana actions such as or Sacrifice a creature), Training Grounds simply wont affect it
Theros drew on Greek myth, following Elspeth's tragic confrontation with the god Heliod
Standard, for example, warps around outliers like overtuned mythics, pushed synergies, or singularly efficient threats, crowding out metagame choices incapable of competing at that level
Take Takeno's Cavalry, a 1/1 for 4 mana that can tap to shoot an attacking or blocking Spirit for a mighty one damage while swinging for one itself (unless its blocked, and then you get a 2/2 for our 4 mana investment)