Griptide

Unsummon hands a creature back to its owner's hand, where it can be recast next turn at leisure. This does worse to the creature for more mana: it tucks the threat onto the top of the library, where it eats the owner's next draw before they can replay it. That landing spot is the whole pitch. Against a freshly resolved threat it is straight tempo, costing the opponent both the cast and the card behind it; against a creature with a problematic enters-the-battlefield trigger or a lingering aura, it merely resets the table without permanently answering anything. The instant timing is what earns the rate: respond to a combat trick, strand an attacker on top of the deck mid-block, or save your own creature from a removal spell by tucking it away (at the cost of redrawing and replaying it). It is not removal, and treating it as such is how players get burned, because the creature comes right back the moment that draw step arrives. What it buys is a turn, and a turn is sometimes the only thing tempo blue is shopping for. The four-mana cost keeps it from becoming a recurring lock piece: you cannot chain it cheaply enough to keep one creature buried forever, so it functions as a one-shot tempo swing rather than a soft prison.