There are seven new cards, but most are filler
Do you prefer Omnath, Locus of RageOmnath, Locus of Rage's fiery power, The Gitrog MonsterThe Gitrog Monster's slippery resourcefulness, Karametra, God of HarvestsKarametra, God of Harvests's reinforced defenses, or Tatyova, Benthic DruidTatyova, Benthic Druid's ever-growing evolution
See also: Master set guide, Binder layout planner What is the total card count for a complete Obsidian Flames master set? A complete master set is 406 cards: 197 base set cards (numbered 1-197), 176 reverse holo versions of the base set cards, and 33 secret rare cards (numbered 198-230)
The more rambunctious Raph & Mikey, Troublemakers come together to make a seven mana 7/7 with trample and haste, who also nets you a creature card from the top of your deck that comes into play tapped and attacking, which is pretty darn good
If Wrenn and One is changed into a basic land type, it continues to be a green Wrenn planeswalker, but it will lose its other abilities