I suppose you could use Vampire Hexmage to reset the clock, if you haven't found your Dark Depths yet
If you sacrifice it, you get to destroy an artifact, enchantment, or even proliferate, making it an excellent choice for counter-based decks
This allows you to keep pace and apply pressure through your army of creatures, but it wont win the game by itself
He is fairly pricey and doesn't do much to protect you against mass removal which is your biggest concern against slower decks
True, replaying the adventure again and again does give you lots of Y'shtola triggers, but it has me wondering whether there's a token subtheme to the deck, or if Hildibrand's ability is only meant to buff his own zombies
The classic is Dark Depths and Thespian's Stage, but theres likely better options these days