how to tell if a yugioh card is ultimate rare Guide to Yu-Gi-Oh! Card Rarity YuGiOh card rarities explained -

As with Skullclamp , Sword of Feast and Famine is very simple

Blink Effects Since the backup ability rests on a creature entering the battlefield, effects that blink the creature can be helpful

Discovery // Dispersal Dogged Detective Dream Eater Duress Extract Brain Hostile Negotiations Invasion of Gobakhan Invasion of Ixalan Jester's Mask Leshrac's Sigil Liliana's Spoils Maestros Charm Mind Slash Narset, Parter of Veils Ostracize Polygraph Orb Professor Onyx Rag Man Sandstalker Moloch Sauron's Ransom Thought Erasure Thran Spider Wail of the Forgotten Warlock Class Withering Gaze Word of Command

These cards could also be the leader of the Commander deck if thats what you chose