Flooded Strand: There are three fetchlands in these sets, and this is the only blue one
Casualties of War Casualties of War isnt a complete board wipe, but this 6-drop sorcery originally from War of the Spark can take out your opponents best permanents
The utility of being able to use this as a (sorcery-speed) pump spell in addition to the fight mechanic was extremely valuable to those decks at the time, which were full of cards like Questing Beast, Lovestruck Beast, Gemrazer, Kazandu Mammoth and other beefy creatures that benefited heavily from fighting
Library Manipulation
The set will also introduce several special new mechanics, including: Job Selection: Heroes can walk various paths, and their equipment can change their destiny
Then there are mash-up commanders like The Archimandrite or Butch DeLoria, Tunnel Snake that combine strange typal synergies together