The strategy of the deck is simple: play turbo fog until you have 6 mana, then play Hive Mind and a pact your opponent can't pay and win the game.
In detail:
Turbo Fog
Cards which prevent damage like Fog, Druid's Deliverance and Haze of Pollen (which can also cycle if we need to find a combo piece in the late game) help us to stay alive. While Howling Mine and Dictate of Kruphix helps us to find them. They may draw our opponent cards, but since they will not be able to attack, this shouldn't matter.
If we are matched against a combo which doesn't win through combat damage, add more counterspells and Angel's Graces. Depending on the exact strategy a Leyline of Sanctity which is mainly in the sideboard for Burn can also help.
Against Control just adding a few more counterspells should be good enough. We only need to ensure that Hive Mind is on the field for a short moment to cast our Pacts.
Hive Mind
This deck has only two ways of winning the game: Deck or opponent (which should be hard) or play Hive Mind
+
Pact of Negation
to give your opponent a die-trigger on their upkeep. Adjusting the Pact according to their mana-base is important, therefore besides all the card draw-effects from the turbo-fog package Tolaria West will help to get the correct Pact for the correct match-up.
Rulings and Misconceptions
It doesn't matter. Either the copy trigger is on the stack or you can now cast your Pact of Negation to give them one. Hive Mind doesn't need to survive for it to resolve.
- My opponent is about to counter my Pact before it's copied!
It doesn't matter. Once the trigger is on stack the original spell can go wherever someone wants it to go and doesn't need to resolve or stay on the stack to resolve. Read the ruling on Mirari.
- My opponent is about to copy Pact of Negation and everything will get complicated!
Yes... Counterspells can't target themself, so their pact needs to target your pact or another spell on the stack. Usually before playing pact you would wait for all other spells and abilities but one to resolve, so they either have to counter that spell (and fizzle your pact) or counter your pact. In both cases you can prevent yourself from paying for your pact, since your Pact of Negation didn't resolve and therefore didn't create a delayed trigger on your upkeep.
- Help, my opponent is about to combo off!
If you have Pact of Negation (or any other pact which can stop them) and Angel's Grace you can use your pact basically for free and Angel's Grace on your upkeep before you would lose the game.
