Now comes the difficult part: between Carmen and Clavileno I actually think Carmen has a much higher power ceiling, but to reach that ceiling you'd need to start moving away from Vampires and into more efficient sacrifice triggers (Pitiless Plunderer) and lifegain payoffs (Archangel of Thune)
Or, at least, it only goes in the 99
Namaari, Morning Mist also has the Blades ability, allowing her to challenge characters who are ready

Abolisher of Bloodlines Abundant Maw All Is Dust Angelic Aberration Anticausal Vestige Artisan of Kozilek Aurora of Emrakul Azlask, the Swelling Scourge Bane of Bala Ged Barrage Tyrant Basking Broodscale Bearer of Silence Benthic Anomaly Benthic Infiltrator Birthing Hulk Bismuth Mindrender Blight Herder Blinding Drone Blisterpod Breaker of Armies Breaker of Creation Brisela, Voice of Nightmares Brood Butcher Brood Monitor Broodwarden Catacomb Sifter Chittering Dispatcher Chittering Host Conduit of Emrakul Conduit of Ruin Corrupted Shapeshifter Cryptic Cruiser Culling Drone Cultivator Drone Deathless Behemoth Deceiver of Form Decimator of the Provinces Deepfathom Skulker Depth Defiler Desolation Twin Devourer of Destiny Dimensional Infiltrator Distended Mindbender Dominator Drone Dread Defiler Dread Drone Dronepack Kindred Drowner of Hope Drowner of Truth Drownyard Behemoth Drownyard Lurker Dust Stalker Echoes of Eternity Elder Deep-Fiend Eldrazi Aggressor Eldrazi Conscription Eldrazi Devastator Eldrazi Displacer Eldrazi Linebreaker Eldrazi Mimic Eldrazi Obligator Eldrazi Ravager Eldrazi Repurposer Eldrazi Skyspawner Eldritch Immunity Emrakul's Hatcher Emrakul's Messenger Emrakul, the Aeons Torn Emrakul, the Promised End Emrakul, the World Anew Endbringer Endless One

If we take this into account, then 45 minutes could pass by in the blink of an eye
In combination with Burnt Offering and Animate Dead or Dance of the Dead, if you could get it into your graveyard quick enough, it was a huge source of Mana for Drain Life or Soul Burn