One card I created was the following: Fighting Spirit 1WW Creature Spirit 2/1 Flying Whenever a mystic spell is played, CARDNAME gets protection from the color of your choice until end of turn
While it does half the damage (only dealing one point of pain at a time) Razorkin Needlehead is also half the cost of Sheoldred, The Apocalype - an infamous creature who has terrorized Standard for ages, and one of the most expensive MTG cards Wizards has put out in recent years
Thats less than $50 a deck, despite three out of four costing more than that when bought separately
Some control decks may play a copy of Mystic Sanctuary so thats something to always consider alongside Uro or the odd Snapcaster Although we dont see these decks too often these days, for historic reference: Reanimator: Reanimation targets, Faithless Looting Hogaak: Bridge from Below, Hogaak, Arisen Necropolis, Vengevine, Bloodghast, Gravecrawler, Cabal Therapy Madness: Vengevine, Faithless Looting, Anger NicFit: Cabal Therapy however, really no specific card other than Academy Rector in NixFit builds
It is much less reliable for final rules MTGPress proxy printing became popular because it solved a very specific Magic problem: players wanted a fast way to turn a decklist into printable proxy TLDR Fan-made Magic cards feel real when they follow the same invisible rules that make official cards readable, balanced, and playable