Exploring Lonis, Genetics Expert in cEDH
Lonis, Genetics Expert by Kai Carpenter
New commanders with combo potential are always interesting, especially if they form a two-card combo with a single other card. In the case of Lonis, Genetics Expert that card is Extruder. Extruder allows you to sacrifice any artifact to put a +1/+1 counter on any creature, such as Lonis. Whenever a +1/+1 counter is put on Lonis, such as when you target it with Extruder's ability, you make a Clue, which is an artifact that you can sacrifice to Extruder.
Additionally, each time you sacrifice a Clue to Extruder, Lonis's other ability triggers, allowing you to put a +1/+1 counter on another creature. When you loop this, you get to put any number of +1/+1 counters on every creature you control. Sometimes that will win the game. The combo isn't perfect, but it's not the only combo we can make with Lonis, just the only one that only requires a single card.
The card that really made me interested in Lonis as a commander is Tarrian's Soulcleaver. With the Soulcleaver equipped to Lonis, you put a +1/+1 counter on Lonis whenever an artifact or creature is put into a graveyard from the battlefield, such as whenever a Clue is sacrificed. This means that once Lonis has Tarrian's Soulcleaver equipped, if you have a way to sacrifice Clues, you can do that infinitely, which again, will make Lonis and all of your other creatures infinitely big, but it will also do whatever sacrificing an artifact does for whatever you sacrificed the artifact to.
However, there are more cards that allow you to freely sacrifice artifacts than I'm interested in playing. Piston's Sledge and Thermal Navigator are much weaker than other alternatives, so I'd rather lean on the good options, like Arcbound Ravager, the cheapest creature that can do this which can also be found with creature tutors. There's also Grinding Station, the cheapest noncreature artifact, which has the considerable benefit of being able to mill every card in all of our opponents' decks, and Krark-Clan Ironworks, which allows us to make infinite mana and draw infinite cards by using the mana to activate the ability of the Clue tokens we make and don't sacrifice to KCI. Krark-Clan Ironworks can also be found by Moonsilver Key, which means we can use an additional tutor to find this piece of the combo.
Speaking of finding the combo, the great thing about Tarrian's Soulcleaver is that it costs only one mana, which means you can find it with Trinket Mage, Urza's Saga, and if you want, Artificer's Intuition. I don't think this is necessary because Trinket Mage is easy to find in a green deck, but it is an option if you want it. Since creature tutors, artifact tutors, and land tutors can all eventually find Tarrian's Soulcleaver, it should be very easy to get Tarrian's Soulcleaver onto the battlefield.
Given the number of tutors we'd want to find those pieces, we could easily include some other Simic win conditions, and then it's just a matter of finding and assembling them.
Lonis Combo Cards
Infinite Green Mana
With Kinnan and Tarrian's Soulcleaver you can tap a Clue for 2 mana and sacrifice it to itself, and since sacrificing a Clue doesn't require tapping, this combination will allow you to draw your deck.
Lonis Synergy Pieces
I'm not sure how many of these are actually good enough to play. Benthic Biomancer lets you loot whenever you put a counter on Lonis. Ulvenwald Mysteries makes a 1/1 whenever you sacrifice a Clue, and Scurry Oak makes a 1/1 whenever you put a counter on it, which you can do whenever you sacrifice a Clue. Neither of these goes infinite with Lonis, but if you have them with cards like Earthcraft, Jaheira, or Gaea's Cradle, they give you extra mana, and if you have both of them with Earthcraft you're infinite.
Again, I don't know if these are worth including; they're likely too cute and should just be additional generically good cEDH cards. Submitted here for consideration. Urza, Lord High Artificer is great. You'll have random Clues lying around from evolving Lonis, and it's a mana sink for your infinite mana combos. Agatha's Soul Cauldron is also very good here, since you can easily get counters on lots of creatures, any ability you get on the Soul Cauldron will be great. The Ozolith is another weird one that doesn't combo, but it does generate a lot of value if the game goes long.
Other Useful Bullets
Walking Ballista gives you an infinite mana sink or relevant board control piece that plays particularly well with both Lonis and Agatha's Soul Cauldron, and you can find it with Trinket Mage. Haywire Mite is another good removal spell you can find with Trinket Mage that is also great with Agatha's Soul Cauldron. I'm including Gilded Drake because it belongs in almost every Simic deck. Spellskite protects your combos, Endurance is generically strong interaction, Manglehorn is a necessary bit of protection since this deck is horrible against Dockside Extortionist, and Phyrexian Metamorph is just a great flexible card. Flesh Duplicate would also be on my short list of cards to add if I cut some of the cute stuff above.
Lonis Tutors
That basically covers what this deck is trying to do and how we're going to accomplish it, the rest is just cards we need to play cEDH in the first place: interaction, card advantage, and mana:
Lonis Interaction Suite
Pact of Negation
Dispel
Flusterstorm
Legolas's Quick Reflexes
Swan Song
Cyclonic Rift
Resculpt
Mindbreak Trap
Lonis Card Advantage
Viridian Revel is a decent card draw engine generally, but particularly important in this deck as a bit of a hedge against Dockside Extortionist.
Lonis Fast Mana
The full list is available here.
I suspect this deck won't overtake Kinnan, Bonder Prodigy as the best Simic Commander, but it's a pretty cool change of pace and it's nice not to have to put a bunch of unreasonably expensive creatures in your deck.
Incidentally, Lonis doesn't have to be your commander to warrant consideration, particularly because it goes infinite with Rosie Cotton of South Lane and it's probably better at doing that than Scurry Oak if you're in Bant as the output makes all of your creatures infinitely big rather than making infinite 1/1s, and you also end up with infinite Clues, which is particularly good if you're playing cards like Jaheira or Urza anyway. One deck that's interested in including this combo is The Third Doctor/Sarah Jane Smith-my personal build of this deck is currently on the high power casual side of things, but I do think it's a pair with competitive potential.