Milling became so popular that it's now common to see entire decks built around the keyword
Like most Magic: The Gathering cards, the value of Gate Colossus 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 (Commander Legends: Battle for Baldur's Gate)
If you want more protection, you can double up and run both Boots and Greaves
Or you can just add him to every kindred deck with his color too
Any opponent who wants to challenge this character will have to discard their full hand to do so, making it hard to stop her effective lore generation without a Banish card or a major sacrifice
If enough creatures die during a single turn, it transforms into Sephiroth, One-Winged Angel, the final major boss of FF7