Allies can attack opposing heroes or allies, but can also be attacked
In general, if your deck can support the colors for a scavenge card, you've got no real reason to avoid playing it
These are just some promos Ive collected from attending Grand Prixes over the years
Lorcana The First Chapter Booster Pack 16 In this pack, we got: Commons: Captain Hook Forceful Duelist, Sudden Chill, Yzma Alchemist, Stitch New Dog, Sergeant Tibbs Courageous Cat, and Aurora Briar Rose Uncommons: One Jump Ahead, Jumba Jookiba Renegade Scientist, and Sven Official Ice Deliverer Rare or above: A Whole New World (Super Rare), and Sword Of Truth (Rare) Foil: Megara Pulling The Strings (Common) An above-average pull with the Super Rare, but it is a great Super Rare
There's also a few odd pricey cards out there like Copy Enchantment and Vesuva that would make for a great reprint as well