Because Arna is capable of doubling counters, as well as copying auras and equipment, there are numerous interesting directions a deck builder can take
It also has a Shift cost of five
As for creatures which have better power/toughness, let me recommend Commander Eesha, Emeria Angel, Guardian Seraph, and Shalai, Voice of Plenty over Aven Trooper
You could go further by pairing it with cards that exile opposing graveyards so only you reap the benefits of the next two chapters
Like u/yOB-LEd, who said: "I never realised this, nice post :)" Redditor u/Lv1FogCloud also admired the illustrator's creativity, especially when it came to hiding the Pokeballs in the art: "Hiding them in sparkles and bubbles was so fun and smart." Some commentators did point out that Saya Tsuruta's career as an illustrator extended beyond Pokemon TCG Pocket
Tyranitar has the potential to deal a ton of damage, we just need to find a way to accelerate Energy more efficiently