Deathrite Shaman The infamous 1-mana planeswalker, life loss is arguably the second most vital of Deathrite Shamans abilities, right behind the mana ability that makes excellent use of fetch lands
Jeskai Fires A dangerous deck when its namesake is in play, this combination uses Fires of Invention to set up explosive turns with Cavalier of Gales , Cavalier of Flame , and other significant threats
Essentially the only difference is that as you advance in the ranks, you, in addition to the standard rewards also unlock ranking rewards
Toxic is the same as poisonous, which appeared on two cards from Future Sight , just developed with a new name, more cards, and the right context
Elementals can get pretty pricey, so 5 mana is often a cost reduction, and at instant speed, you can pull a lot of surprises outside your turn