( You may cast a spell for its freerunning cost if you dealt combat damage to a player this turn with an Assassins or commander .) Whenever Ezio deals combat damage to a player, you may pay WUBRG if that player has 10 or less life
The other huge upgrade that isn't a Vampire is, of course, Skullclamp, which if you're lucky enough to find / stick on the battlefield will draw you all the cards you need to close out the game
For instance, if Nahiri, Storm of Stone is on the battlefield, Nicol Bolas deals the damage if you activate the ability he gained from her
So Nissa becomes less of a combo piece and more of a reliable power/toughness engine in your grindy GBx deck
This will also turn your dorks into an Ancient Greenwarden and play lands from your graveyard, Carnage Tyrant to make it a beater, Grunn, the Lonely King to double its power when it swings alone, Kamahl, Fist of Krosa to Overrun and make lands dorks, Multani, Maro-Sorcerer to grow massively in size and get shroud, Nemata, Grove Guardian to make a bunch of tokens, Primordial Sage and Soul of the Harvest to draw cards, Rampaging Baloths to landfall and game win, and that's just one casting cost
This feels more like duck hunting, but however you look at it, you'll want to give Haldan some evasion and possibly use a tool like Strionic Resonator to double his triggers