You can now create own custom Pokemon cards using templates from Pokemon TCG Pocket and Pokemon first generation
Even from the beginning, particularly powerful and/or rare cards were not uncommon, and as the franchise grew and hundreds of new creatures were added to the Pokedex, each batch came with something more rare and powerful than ever before

Frogs Clement, the Worrywort 39%inclusion 1.47K decks 3.80K decks Grolnok, the Omnivore 23%inclusion 876 decks 3.80K decks Glarb, Calamity's Augur 23%inclusion 865 decks 3.80K decks Tatsunari, Toad Rider 5.0%inclusion 191 decks 3.80K decks Helga, Skittish Seer 3.0%inclusion 113 decks 3.80K decks Flubs, the Fool 1.2%inclusion 45 decks 3.80K decks Morophon, the Boundless 0.8%inclusion 29 decks 3.80K decks Quina, Qu Gourmet 2.0%inclusion 18 decks 918 decks Sab-Sunen, Luxa Embodied 1.5%inclusion 18 decks 1.16K decks Yargle and Multani 0.3%inclusion 12 decks 3.80K decks Muldrotha, the Gravetide 0.3%inclusion 10 decks 3.80K decks The Gitrog, Ravenous Ride 0.2%inclusion 9 decks 3.80K decks Berta, Wise Extrapolator 1.8%inclusion 9 decks 490 decks Thalia and The Gitrog Monster 0.2%inclusion 9 decks 3.80K decks The Gitrog Monster 0.2%inclusion 6 decks 3.80K decks Rukarumel, Biologist 0.1%inclusion 5 decks 3.80K decks Atraxa, Grand Unifier 0.1%inclusion 5 decks 3.80K decks Ms

Mirrorpool's third ability can target (and copy) any instant or sorcery spell, not just one with targets
The trick here is that you don't have to use it on YOUR attacking creature
Saheeli, the Gifted is a fine commander, with her ability to add a bunch of mana with her second +1 being especially scary, but she suffers from the fact that there are a bunch of artifact-based Commanders available, including the extremely powerful Breya, Etherium Shaper, so being "fine" might not be enough to pick Saheeli, the Gifted as your Commander over other options