It gives you (your ally) +1 health and + 1 sanity for $1 without the need of spending the cost of an action
I counted all the differences: take the 38,768 unique cards, account for 58,779 in additional foils and treatments, plus 718,172 non-English cards, 5,278 non-playables (the tokens, art cards, etc.), 755 playtest cards, Arena's 221,930 cards in their languages, and 29,252 MTGO cards and you arrive at our total of 1,072,934
Investigation, puzzle solving, and deep stories
These aren't tournament-legal (they come with a distinct card back pattern), but they're excellent reference points for competitive players and popular collector items for anyone who follows the competitive scene
When you do, add its power to this creatures until end of turn.) Whenever a creature you control attacks, if it enlisted a creature this combat, the creature that attacked gains double strike until end of turn
For more controlling builds, copying Spine of Ish Sah allows you to destroy a permanent every turn, while the sacrifice trigger returns the original Spine to your hand for repeated use