Averna, the Chaos Bloom was the first of many Legendary creatures from Commander Legends that we were very exciting to build around.
First, let's jam in every single spell in Temur colors that has Cascade, since they each basically get Rampant Growth attached to them and we want to increase our probability to go off with a huge chain. It's worth noting that we can swap in Maelstrom Wanderer as our Commander once in a while if we feel like changing it up.
1 Annoyed Altisaur 1 Apex Devastator 1 Aurora Phoenix 1 Bloodbraid Elf 1 Boarding Party 1 Etherium-Horn Sorcerer 1 Forceful Denial 1 Garbage Elemental (A) 1 Imoti, Celebrant of Bounty 1 Ingenuity Engine 1 Maelstrom Colossus 1 Maelstrom Wanderer 1 Meteoric Mace 1 Natural Reclamation 1 Sakashima's Protege 1 Shardless Agent 1 Sweet-Gum Recluse 1 Throes of Chaos 1 Violent Outburst 1 Volcanic Torrent
Now let's find a bunch of sweet landfall payoffs to take advantage of our abundance of mana and actual lands entering the battlefield:
1 Tayova, Benthic Druid 1 Scute Swarm 1 Lotus Cobra 1 Moraug, Fur of Akoum 1 Avenger of Zendikar 1 Rampaging Baloths 1 Omnath, Locus of Rage 1 Aesi, Tyrant of Gyre Strait - Foil - Theme Deck Exclusive 1 Phylath, World Sculptor 1 Roil Elemental 1 Omnath, Locus of the Roil 1 Tireless Tracker 1 Valakut Exploration 1 Zendikar's Roil 1 Primeval Bounty
Now let's take a look at some cool synergies with our cascade deck: things that benefit from casting multiple spells, things that let us arrange the top cards of our deck, and spells that are good to cascade into.
1 Cavalier of Gales 1 Animar, Soul of Elements 1 Brainstorm 1 Release to the Wind 1 Ancestral Vision 1 Mind's Desire 1 See the Truth 1 Baral's Expertise 1 Portent 1 Crystal Shard 1 The Great Henge 1 Temur Ascendancy 1 Rhythm of the Wild 1 Remand
We can round out the deck with some generic goodstuff that gives us a normalized curve to maximize the chance that we get high value off of our cascades. We don't need to spend as many slots on random ramp spells as you would typically find in a Commander deck since Averna does most of that for us. Here's a few notable cards that we think work well in this deck:
1 Sunbird's Invocation 1 Rashmi, Eternities Crafter 1 Coiling Oracle 1 Eternal Witness 1 Terror of the Peaks 1 Risen Reef 1 Beast Whisperer 1 Growth Spiral 1 Rishkar's Expertise 1 Urban Evolution 1 Preordain 1 Guardian Project 1 Explore
And finally a quick drop of some notable and/or inexpensive lands for this deck:
1 Field of the Dead 1 Reliquary Tower 1 Temple of the False God 1 Mosswort Bridge 1 Alchemist's Refuge 1 Castle Garenbrig 1 Kessig Wolf Run 1 Castle Vantress 1 Command Tower 1 Ketria Triome 1 Rootbound Crag 1 Hinterland Harbor 1 Sulfur Falls 1 Frontier Bivouac 1 Cinder Glade 1 Temple of Mystery 1 Temple of Epiphany 1 Temple of Abandon 1 Gruul Turf 1 Simic Growth Chamber 1 Izzet Boilerworks 1 Path of Ancestry 1 Halimar Depths
One deckbuilding note is that it could also be possible to build this deck with an extremely high land count in order to increase the probability of chaining cascade spells into each other. Over the years as more cascade spells are created (which may happen slowly but surely), this deck will get even better, but it seems very powerful already!