Character cards are used to defeat ones that your opponent plays and earn Lore that you need to win the game
Kaladesh will have its fair share of countermeasures for its own cards, and one in particular stands out to me as more powerful than the rest: Demon of Dark Schemes
Condition is king when it comes to deciding the worth of collectibles, and Pokemon cards from any region are no different

Argentum Masticore Aurora Eidolon Bant Sureblade Basri's Lieutenant Brace for Impact Cloven Casting Depopulate Dragon Arch Enemy of the Guildpact Enigma Eidolon Entropic Eidolon Esper Stormblade Fallaji Wayfarer Frenemy of the Guildpact (playtest) General Ferrous Rokiric Ghostfire Slice Glass of the Guildpact Glittering Wish Gloryscale Viashino Grixis Grimblade Guildmages' Forum Guildscorn Ward Hero of Precinct One Infinite Guideline Station Jared Carthalion Jenson Carthalion, Druid Exile Jund Hackblade Knight of New Alara Lilah, Undefeated Slickshot Lobber Crew Mage Tower Referee Mana Cannons Maze Abomination Maze Behemoth Maze Glider Maze Rusher Maze Sentinel Naya Hushblade Neutralizing Blast Niv-Mizzet, Guildpact Null Elemental Blast Obscura Charm Obsidian Obelisk Pillar of the Paruns Psychotic Fury Pure // Simple Pure // Simple Pyroconvergence Radiant Purge Rampaging Monument Ravnica at War Reborn Hope Renounce the Guilds Rewards of Diversity Rienne, Angel of Rebirth Sandstorm Eidolon Scuttling Butler Shatter Assumptions Soldier of the Pantheon Spectrum Sentinel Stonecoil Serpent Stormscale Anarch Supply // Demand Supply // Demand The Mana Rig Tome of the Guildpact Trial // Error Trial // Error Urza's Filter Verdant Eidolon Vivid Revival Widespread Thieving

A 4/4 Golem for five mana that gets -4/+4 whenever it blocks or becomes blocked, the key appeal of Karn is the manner in which it interacts with your other artifact cards
And that's before we even go looking for cards that break it like the nameless Elvish Archdruid or Gilt-Leaf Archdruid