there are just too many viable decks and too many fringe strategies out there
Buried cards are placed facedown in an area off to the side, never to be played again during the game
Then if you control five or more Ninjas, that player loses half their life, rounded up
It combines with Corpse Knight and Smitten Swordmaster for extra reach and grinding potential late game, and enables evasive beaters like Order of Midnight and Stormfist Crusader
In other words, Achilles will come down for its reduced cost often, provide a decent threat, and buff your entire board as long as he remains on the battlefield
One neat trick to remember about is that you can cast it to destroy an Urzas Saga with its first lore counter trigger on the stack, which means your opponent would not get the chance to tap the land for mana