Sliverguy420 Oops, I wrote down the wrong thing. Thanks for correcting me! =)

Siege-, well, this is a good time to learn. =)

A "format" is basically a set of rules about what cards you can play and how many of them. The formats are mostly gated chronologically -- which is important, because the "older" a format is, the more broken cards it has access to. "Legacy" has a cut-off of, basically, "None, any card ever printed is legal... which means we have access to recent losers like Merfolk of the Depths, sure, but also suuuper-powerful cards that cost four figures (Tropical Island, Ancestral Recall)." And when you say your deck is in the Legacy format, you're saying, "Yeah, I want my deck to be considered alongside decks with those kinds of cards," which... might be misleading. =)

Your deck is Modern-legal, meaning it only uses cards that were printed after the game's first ten years. (Any Modern-legal deck is, by definition, also Legacy-legal, but that still doesn't mean they can compete with each other.) It's also close to being Pioneer-legal (meaning it only uses cards that were printed after the game's first twenty years), though you'd have to give up Treefolk Umbra and I know you're attached to that. You're not required to make it compliant to any format, particularly since you and your friends clearly play using house rules; I'm simply trying to help you understand what claims you're currently making.

Two cards I would advise you: Generous Gift and Growth Spiral. Both would fit in nicely.

Why is this marked as a Legacy deck? It seems to be Modern-legal to me. =)

I love the way you approach deckbuilding. You take this silly junk idea and figure out how to make it work. This deck is so silly that it should be fun to lose to -- I don't think a deckbuilder can aspire to anything greater.

Looking at a rudimentary Scryfall search, I see a number of cards that could replace Autochthon Worm for effect and at a lower dollar value: Rust Goliath, Woodcaller Automaton, Ancient Stone Idol, Decimator of the Provinces, Shadow of Mortality, Thrasta, Tempest's Roar, Explosive Singularity and Volcanic Salvo are all MV 10 or higher and (as of this writing) $1 or less. The latter two are harder to fetch with your infrastructure, but have the added benefit of being other ways to potentially finish off the opponent... though the odds of surviving long enough to hardcast them seem remote.

Saving $8 only goes so far, but you know me: always looking for the monetarily cheapest execution of an idea. And I love this idea.

This costs so much money, but it's so much fun to play!!