You might not have as many creatures as Marie-Lise does, but you do have a way to get past her blockers: Holy Mantle. The problem is that it’s currently hidden under your Mosswort Bridge, and there’s still the matter of producing a creature large enough to wear it.

There’s also another problem in that you don’t have enough green mana to see you through: Your Nature’s Claim, Terravore, and Mosswort Bridge will all need a specific color to cast or activate. What you do have, however, is a way to create more sources of green mana: Riftstone Portal.

1. Tap Llanowar Reborn to add to your mana pool.
2. Tap Riftstone Portal to add to your mana pool.
3. Spend to cast Nature’s Claim on your Phyrexian War Beast. You gain 4 life. You are now at 14 life.
4. When Phyrexian War Beast leaves the battlefield, its ability triggers. Choose to sacrifice Riftstone Portal. Phyrexian War Beast deals 1 damage to you. You are now at 13 life. Now that Riftstone Portal is in your graveyard, all lands you control can tap to produce green or white mana.
5. Tap Arena and Cathedral of War to add to your mana pool.
6. Tap Hall of the Bandit Lord and pay 3 life to add to your mana pool. You are now at 10 life.
7. Spend and the from Hall of the Bandit Lord to cast Terravore. Terravore enters the battlefield with haste, and is 1/1 due to the Riftstone Portal in your graveyard. (You still have in your mana pool from Riftstone Portal.)
8. When Terravore enters the battlefield, choose to use Llanowar Reborn’s Graft ability, moving a +1/+1 counter from Llanowar Reborn to Terravore. Terravore is now a 2/2 creature.
9. Tap and sacrifice Ruins of Trokair to add to your mana pool. Terravore is now a 3/3 creature.
10. Spend to activate Rustic Clachan’s Reinforce ability, discarding it and putting a +1/+1 counter on Terravore. Terravore is now a 5/5 creature.
11. Play Karoo. Since you can’t return an untapped Plains to your hand, you are forced to sacrifice Karoo. Terravore is now a 6/6 creature.
12. Tap Yavimaya Hollow to add to your mana pool.
13. Because you now have seven cards in your graveyard (Blastoderm, Nature’s Claim, Phyrexian War Beast, Riftstone Portal, Ruins of Trokair, Rustic Clachan, Karoo), you may now spend to activate Nantuko Monastery’s second ability, turning it into a 4/4 creature.
14. Tap Nantuko Monastery to add to your mana pool.
15. You now have 10 power among creatures you control (6/6 Terravore, 4/4 Nantuko Monastery), so you may now spend and tap Mosswort Bridge to activate its second ability. Choose to play Holy Mantle on Terravore. Terravore is now an 8/8 creature with haste and protection from creatures.
16. Declare the start of your combat phase, assigning Terravore as your lone attacker.
17. Cathedral of War’s Exalted ability triggers, giving Terravore +1/+1 until end of turn. Terravore is now a 9/9 creature.
18. Marie-Lise is unable to block Terravore due to Holy Mantle’s protection ability. Terravore deals 9 damage to her, defeating her.