• Not sure if Wotc like vacuously true statements for cards like Kaheera, the Orphanguard.
• Provided Lurrus of the Dream-Den doesnt get banned 10000% recommend it as the companion, beacuse it helps with removal on your enchantment.
• Yorion, Sky Nomad is used in competive play however in this deck it has no real purpose.
• reducing activatied abilites only help with cards with a mana cost to those abilites. Dont recommend

Zirda offers a powerful option; Umbral Mantle combo. Once the cat nightmare is banned, I'd look at it.

With an animated manland, a reduced cost untap, and zirda, you can make that manland arbitrarily large, usually without forecasting the combo. Since your treasure hunt should make finding it simple, and manland support will benifit the deck anyway, it seems like a very low-cost sideboard plan.