These tell what the energy cost of the attack are
Spring-Leaf Avenger Spring-Leaf Avengers ninjutsu is reasonable enough at 4 mana, and youll get a huge 6/5 that hits with an Eternal Witness effect
(Right now, the most dominant cards in the format have a level of dominance that is unheard of, even including all of the other broken decks and banned cards we've been talking about

Goblin Guide Grim Lavamancer Mogg Fanatic Stromkirk Noble Lightening Bolt Chain Lightening Burst Lightening Lava Dart Reckless Charge Cursed Scroll Seal of Fire Reckless Waif Torch Fiend Hellspark Elemental Keldon Marauders Ember Hauler Kargan Dragonlord Incinerate Arc Trail Searing Blaze Sulphuric Vortex Brimstone Volley Fireblast Chandra's Phoenix Teetering Peaks Barbarian Ring 14 Mountains Other good RDW cards: Goblin Bushwhacker Spikeshot Elder Koth of the Hammer Chandra, the Firebrand Wheel of Fortune Sac lands Wasteland Boggart Ram-Gang Figure of Destiny Manic Vandals Bonesplitter Tanglewire Chaos Warp Slagstorm (from the B cube) Stigma Lasher Magus of the Scroll Firebolt Jackal Pup Shrine of Burning Rage Ball Lightening Gorilla Shaman Plated Geopede Black Vice The core framework of the deck is built around the following few cards

Espers to Magicite This fun instant speed Black four-cost will exile all enemy graveyards and then you can bring one exiled dork back as an artifact token under your control
Sliversmith Sliversmith may only make a 1/1, but in a sliver deck any single sliver is going to become very powerful