yugioh card black luster soldier Yu-Gi-Oh! MR-055 – Must be Ritual Summoned Black Luster Soldier - Soldier

Where you go with it from there is up to you, but its a great way to create a proof-of-concept card for a friend or actually create custom cards to proxy and play with

Once per turn: You can activate 1 of these effects: -Reveal 1 monster that lists "Dark Magician" or "Eye of Timaeus" in its Text

It has a Freerunning cost of one generic and one black (You may cast this spell for its freerunning cost if you dealt combat damage to a player this turn with an Assassin or commander.) Destroy target creature

There are also cards that change power and toughness, like Brine Hag for opposing creatures or Arni Brokenbrow for your own