Sword of the Animist, Colossus Hammer, Blackblade Reforged, Mantle of the Ancients, and Bear Umbra all make for a pretty solid way to strengthen your knights
My point is this: you have to think about it in the context of your own deck
If you care about this effect, you probably want this card
Try thinking about the buying/selling pace that would match your personality (modern, mid, vintage, slow, fast, English, Japanese) and then finding a single set, or even a single Pokmon or single card that matches
Flying The Darkness Crystal Rarity: Rare TYPE: Legendary Artifact SUBTYPE: - CMC: 4 Mana cost: USD: $9.92 EUR: 5.80 TIX: 0.00 EDHREC RANK: 1314 Black spells you cast cost less to cast
Despite a relatively high known population of this card, with PSA having graded 2,621 copies of 1st Edition Holographic Blastoise, only 101 were graded PSA 10, while 645 copies were graded near mint