mtg search your library for a sorcery card Mystical Tutor [Signature Spellbook: Jace] All cards will be carefully packed for safe transit Rules Text: Search your library

Each Play Booster contains 14 Magic: The Gathering cards and 1 Token or Art card, including 14 cards of rarity Rare or higher and 35 Uncommon, 69 Common, and 1 Land cards

I prefer Time Elemental to Boomerang because its effect can be recurred indefinitely from the permanent itself, rather than a one-time-use instant

It has a splashy effect that is viable in no other format but Commander, and Scourge allows you to dabble in the politics of Commander games (unlike say, Thundermaw Hellkite who just Hulk smashes an unfortunate opponent)

All aggro decks in red color will want this, but especially werewolves and humans due to tribal synergies

You will want to add cards to help make them unblockable like Rogue's Passage to get the card flow and player kill

Death Baron Death Baron is a wonderful skeleton and zombie lord card