While Merfolk Secretkeeper and Wall of Lost Thoughts might be a bigger body to cushion blows, their milling ability only triggers once
Sorceress's Schemes is a red uncommon that pulls other instants or sorcery cards out of the graveyard or even exile, and - with the right helpers - creates an infinite loop that will ping your opponent to death
For example, even if we interpreted your library as part of the battlefield for this purpose, slipping one into the card sleeve of a card in your library during a search effectively marks your deck, and that's not allowed
Lowering your own creatures' toughness may sound counterintuitive, but it's an incredible way to set off those death triggers and draw lots and lots of cards
At the beginning of your upkeep, if Master of Death is in your graveyard, you can pay a life to put it back into your hand
Extended-Art Cards Extended art is also a treatment unique to Collector Boosters