You look for mill-related cards like Mesmeric Orb or Mindcrank which can affect everyone instead of target opponent mill X cards. You may need very specific combos like Fleet Swallower with Bruvac the Grandiloquent, which mills all of a certain players cards
Like most Magic: The Gathering cards, the value of Collector Protector depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Unhinged)
And here some more examples from the collection of @fritz
1 Markov Baron
Far // Away, Turn // Burn, and Unflinching Courage are selling for $1
Wrap Up Idol of the Deep King | Illustration by Matteo Bassini I like the craft mechanic very much, and enjoy the challenge to play with it, both in Limited and Constructed