This 69-card expansion set adds more Mega Evolution Pokmon to the pool, including the Mega Evolutions of the Kanto starters
One is similar to the normal stamp you see on foils: When I shopped I had the option of one that looks more like the Universes Beyond style triangle: I guess you are supposed to stick these on the bottom of your proxies after you get them

Elemental Mascot Elemental Masterpiece Elemental Summoning Emberwilde Caliph Enigma Drake Enthusiastic Mechanaut Epic Experiment Eris, Roar of the Storm Eruth, Tormented Prophet Essence Backlash Etherium-Horn Sorcerer Exalted Flamer of Tzeentch Expansion // Explosion Expansion // Explosion Experimental Overload Expressive Iteration Farideh, Devil's Chosen Fearless Swashbuckler Fell Beast's Shriek Fevered Visions Firemind's Foresight Firemind's Research Firestorm Hellkite Firkraag, Cunning Instigator Flame of Anor Flaring Cinder Fluxcharger Frenetic Efreet Frenetic Sliver Frost Fair Lure Fish Frostburn Weird Frostcliff Siege Gadget Technician Galazeth Prismari Galvanic Iteration Gandalf the Grey Gandalf's Sanction Gelectrode Ghyrson Starn, Kelermorph Gitaxian Spellstalker Glacial Dragonhunt Gleaming Geardrake Goblin Electromancer Goblin Flectomancer Goblin Test Pilot Hawkeye, Avenging Archer Heaven Sent Herald of Kozilek How to Keep an Izzet Mage Busy (playtest) Hustle // Bustle Hypersonic Dragon Hypothesizzle Ian Malcolm, Chaotician Iceman and Firestar Idris, Soul of the TARDIS Ill-Timed Explosion Improbable Alliance Inside Out Inspired Skypainter Intruding Soulrager Invade the City Invasion of Kaladesh Invasion of the Giants Invert // Invent Invert // Invent Invert Polarity Invoke the Firemind Ionize Iron Lad, Young Avenger Iron Man, Master of Machines Iron Man, Titan of Innovation Izzet Charm

At least a spell that puts lands into play is usually thinning your deck so you are improving your odds of drawing an impactful card next turn
Chart shows the price of Pikachu [Reverse Holo] #35 at the end of each month going back as long as we have tracked the item.