Aboleth Spawn Abomination Abomination of Gudul Abomination of Llanowar Abyssal Gatekeeper Abyssal Gorestalker Abyssal Horror Abyssal Nocturnus Advanced Stitchwing Ahriman Ancient Cellarspawn Angel of Suffering Appendage Amalgam Arcbound Fiend Armaggon, Future Shark Arvinox, the Mind Flail Ashiok's Reaper Ashiok's Skulker Atraxa, Praetors' Voice Awoken Horror Balefire Liege Banehound Bedlam Reveler Blistergrub Bloodcurdler Boneshard Slasher Boneyard Lurker Braids, Arisen Nightmare Brainstealer Dragon Braska's Final Aeon Brokkos, Apex of Forever Bruna, the Fading Light Cabal Therapist Canker Abomination Captain N'ghathrod Carnival Carnivore Carnival Hellsteed Carrion Locust Cateran Brute Cateran Enforcer Cateran Overlord Cateran Slaver Cavern Whisperer Chained Throatseeker Chasm Skulker Childhood Horror Chittering Harvester Chittering Host Chupacabra Echo Clammy Prowler Cleaver Skaab Comet Crawler Conduit of Storms Consuming Aberration Core Prowler Corrupted Harvester Cosmic Horror Crawling Chorus Creakwood Liege Creeping Inn Cruel Somnophage Cruel Witness Crypt Lurker Cryptborn Horror Culvert Ambusher Cursed Monstrosity Cursed Wombat Dark Hatchling Dauthi Horror Deathbonnet Hulk Deathbringer Liege

Nobles are crafty little things
The non-legendary one is a 2/2 for four that gives your Black stuff the Bad Moon boost
The Fire Crystal certainly seems the best of the bunch in a vacuum, thanks to offering effects that are interesting for a multitude of different strategies
So stuff like Restoration Angel and Flickerwisp are fine with me b/c they're serviceable on their own, but the techier pieces often have too much of a set-up cost or lend themselves to narrow strategies
Granting haste to all creatures and increasing the mana produced by basic lands can lead to very fast turns, but those benefits apply to everyone, not just you