Dark Depths by itself is a threatening and imposing card, but theres a fun combo with Thespian's Stage where the copy technically doesnt come into play, so it already has no counters and immediately places the Marit Lage token into play
And if that's not enough, she has partner so you can choose the most powerful adjunct colors and concepts
With prowess cards and Boros Charm, you might get tired of taking 3 to the face and losing pretty soon
Card advantage is, very likely, the single most important concept in competitive Magic
Casting instants is arguably the best use of prowess, as it means I can buff my prowess creatures during combat or even during my opponents turn
Reconstruction Reconstruction is also from Antiquities , but you wouldnt know it since every Antiquities printing of this card is missing the MTG set symbol