Keep seven unless the hand cannot do its job

The London mulligan lets you look at seven, put cards on the bottom equal to how many times you sent it back, and keep going. The cost is real — you are down a card — but it is smaller than the old Vancouver rule. Players responded by shipping hands they should have kept.

A keep is not a pretty hand. A keep is a hand that can execute your plan against a reasonable draw from the opponent.

If you are the beatdown, you need a start that spends mana on the first three turns and applies pressure. Two lands and a pile of fives is not a keep because the gold-bordered rares are expensive. One land and two one-drops can be a keep if the deck is built to hit land two. Know which deck you are.

If you are the control, you need enough land to turn the corner and at least one piece of interaction before you die. Six land and a win condition is often a mulligan. Zero interaction against a linear deck is a mulligan even if the mana is perfect.

The bottoming step is not a second deckbuilding exercise. Put back the cards that are dead in the first four turns, or the extra copy of a spell you cannot cast yet. Do not bottom your only two-drop because you want to “see more gas.”

Going to five is a different game. You are looking for a hand that does something on curve, not a hand that wins. If you cannot describe the first three turns after you bottom, send it back one more time. If you can, stop.

The common leak is vanity. People mulligan a slightly awkward seven because they have seen a god hand in testing. Your opponent is not testing. Play the seven that functions.