pokemon card sigilyph Japanese 035/086 sv11W U Mirro Monster Ball TCG — ToysOneJapan Attack 2 Sigilyph - 123/264 (SWSH08) Common

Considering that both cards are in print and, discounting the Aftermath debacle, is from Magic's newest set, I'd lean towards selling while prices are high unless you plan on building the deck yourself

A: Yes, if you believe it has a 9+ potential

Angel's Grace Celestine Reef Cloudsteel Kirin Courageous Resolve Gideon of the Trials Herald of Eternal Dawn Lich's Mastery Liliana's Other Contract (double-faced)(playtest) Platinum Angel Platinum Angel Avatar The Book of Exalted Deeds

doing the best with what you've got

While some hyper efficient, single-target interaction like countermagic and Path to Exile is useful, you should also invest in cards like Grasp of Fate, Soul Shatter, and Convert to Slime to keep ahead on cards while putting your opponents behind on the board