Thats the oops every planeswalker wants to avoid.
MTG Hexproof history The effect of MTG's Hexproof keyword first appeared on a couple of cards in 1999's Portal Three Kingdoms set
Invasion of Mercadia C-Tier: Basically the battle version of Bitter Reunion, except the ability to give all of your creatures haste is likely more of an upside than potentially flipping into a 3/3, which means this is probably just a worse version of a card that already exists

Scientists Aang, Master of Elements Aclazotz, Deepest Betrayal Action News Crew Adventurer's Airship Aether Syphon Agency Coroner Agent 13, Sharon Carter Agent Maria Hill Agent Venom Agna Qel'a Agonasaur Rex Ahriman Air Nomad Legacy Airbending Lesson Airship Crash Airship Engine Room All-Fates Scroll Alpharael, Dreaming Acolyte Alquist Proft, Master Sleuth Altanak, the Thrice-Called Ambling Stormshell Ancestral Reminiscence Angler's Shield Anticausal Vestige April O'Neil, Hacktivist April, Reporter of the Weird Arbiter of Woe Arcane Epiphany Arcanis the Omnipotent Archmage of Runes Ashiok's Reaper Astrologian's Planisphere Atlantean Cavalry Attuma, Atlantean Warlord Audience with Trostani Auspicious Arrival Avengers Assemble
More than six legs or fewer than two, and youre out