And in the worst case scenario, you could grab an opposing blocker and turn it into your attacker so your forces could come in for the win
You can play it when theres one opposing creature, and then the creature will die at the start of your opponents turn
I do not have Pact of Negation in my cube presently however its value rapidly increases as the number of suitable archetypes for it increases and with cube design being as diverse as it is you can easily include more of those archetypes from one of a few different approaches
When 70% of instants and sorceries in my cube are 1 or 2 mana and the average CMC of such cards is about 2.5 (realistically a lot lower as so many of the high cost cards have delve or pitch and alternate costs) you start to appreciate how good four mana and higher spells must be
Card TypeLegendary Creature Nightmare RarityRare At the beginning of your end step, you may sacrifice an artifact, creature, enchantment, land, or planeswalker