Karn is however a very potent card overall offering lots of off colour things to whoever wants them

Ashcloud Phoenix Aven Cloudchaser Cinder Cloud Cloud Cover Cloud Crusader Cloud Djinn Cloud Dragon Cloud Elemental Cloud Key Cloud Manta Cloud Pirates Cloud Spirit Cloud Sprite Cloud of Darkness Cloud of Faeries Cloud's Limit Break Cloud, Ex-SOLDIER Cloud, Midgar Mercenary Cloud, Planet's Champion Cloudblazer Cloudbound Moogle Cloudchaser Eagle Cloudchaser Kestrel Cloudcrest Lake Cloudcrown Oak Cloudfin Raptor Cloudform Cloudgoat Ranger Cloudheath Drake Cloudhoof Kirin Cloudkill Cloudkin Seer Cloudpiercer Cloudpost Cloudreach Cavalry Cloudreader Sphinx Cloudsculpt Technician Cloudseeder Cloudshift Cloudshredder Sliver Cloudskate Cloudspire Captain Cloudspire Coordinator Cloudspire Skycycle Cloudsteel Kirin Cloudstone Curio Cloudthresher Death Cloud Hypnotic Cloud Krosan Cloudscraper Lifted by Clouds Lightning Cloud Meloku the Clouded Mirror Najeela, the Blade-Blossom Nyxbloom Ancient Oboro, Palace in the Clouds Oltec Cloud Guard Pride of the Clouds Riftwing Cloudskate Sea of Clouds Shepherd of the Clouds Skycloud Egg Skycloud Expanse Soratami Cloud Chariot Soratami Cloudskater Spore Cloud Stormcloud Djinn Stormcloud Spirit The Western Cloud Thundercloud Elemental Thundercloud Shaman Untaidake, the Cloud Keeper

Then you counter the first sorcery, instant or artifact your foes cast each turn, which is nastier in multiplayer
Arguably more importantly, all Scion and Spawn creatures you control get indestructible and annihilator 1 until the end of the turn and given the way this deck can and will be able to spit out those tokens, those annihilator triggers can become a problem fast
Illustrated by Chris Rallis Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Legal Comp
Enchantment - Class Pollywog Prodigy Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.) Whenever an opponent casts a noncreature spell with mana value less than this creature's power, draw a card