In May 2022, a dollar that promised to always be worth a dollar became worth twelve cents in three days. About sixty billion dollars of value — gone. Not stolen by a hacker. Not seized by a state. It simply evaporated, exactly as its design permitted, the moment enough people asked it to prove the thing it kept promising.
That was Terra's UST. And its collapse is the cleanest lesson in crypto about a single question you have to be able to answer before you touch any stablecoin: when you want out, what is actually on the other side of the door?
Three ways to pin a dollar
A stablecoin is a token that tries to stay worth one dollar. There are only three honest ways to do it, and they are not equal.
Fiat-backed. For every token in circulation, a real dollar (or a T-bill, or cash) sits in a real account. USDC, roughly, works like this. You want out, you burn the token, you get the dollar. The peg holds because there's a dollar behind it. The catch: you're now trusting whoever holds those dollars — a bank, a custodian, an audit. Centralized, but grounded.
Crypto-backed, overcollateralized. You lock up more than a dollar of volatile crypto to mint one stablecoin. DAI, roughly, works like this. Lock $150 of ETH, mint $100 of DAI. If ETH falls, the system liquidates your collateral before the stablecoin goes underwater. Wasteful with capital, but it has a real cushion. There's something behind each coin, and it's worth more than the coin.
Algorithmic. No dollar behind it. No overcollateralization. Just code and a promise: an algorithm that mints and burns a second token to push the price back to a dollar whenever it drifts. No reserves in the traditional sense. Stability manufactured entirely out of incentives and confidence.
Terra was the third kind. And the third kind has a body count.
The clever machine that eats itself
Terra ran two tokens. UST, the stablecoin, meant to be worth $1. LUNA, the volatile sister token, meant to absorb the shocks.
The mechanism was elegant on the whiteboard. The protocol let you always swap $1 of UST for $1 worth of LUNA, and vice versa — minting one by burning the other.
- If UST traded at $0.99, arbitrageurs would buy cheap UST, redeem it for a full $1 of LUNA, pocket the cent. Buying UST pushed it back up to $1.
- If UST traded at $1.01, they'd burn $1 of LUNA to mint UST worth $1.01, pocket the cent. Minting UST pushed it back down.
Neat. Self-correcting. As long as LUNA had value, the peg had a shock absorber. That was the whole thesis.
See the load-bearing assumption? As long as LUNA had value. The dollar was defended not by a dollar, but by faith in a token whose only real job was to defend the dollar. A snake told to guard the peg by eating its own tail. Fine while everyone's calm. Lethal the second they aren't.
Our record: the Scales of Ma'at need a true counterweight — the feather, a real thing on the other pan. Terra put nothing on the other pan and painted a feather on the empty air. The scale read "balanced" as long as no one leaned on it. Isfet loves a system that looks stable and is only unchallenged. Weightless order is not order. It's a held breath.
Anchor: the yield that had to be paid
Why did anyone hold billions of a weightless dollar? Because Terra bribed them to. A protocol called Anchor offered around 20% yield on UST deposits. Twenty percent. On a "stable" asset. In a world where a bank gives you a fraction of a percent.
Ask the one question that dissolves most crypto: where does the yield come from? Real yield comes from real borrowers paying real interest. Anchor's borrowers didn't come close to covering 20%. The gap was paid out of a subsidy — a reserve that was steadily draining. The high yield wasn't a return on productive activity. It was a customer-acquisition cost, funded by a countdown timer.
So the "stablecoin" was really a high-yield fund that could only pay its yield as long as new money kept flowing in and confidence held. Read that sentence twice. You've read it before, under an older name. When the payout to old participants depends on the inflow of new participants and there's no productive engine underneath — the shape has a name, and it is not "stablecoin."
The death spiral, step by step
In May 2022, large holders started pulling UST out. The peg slipped — $0.99, $0.98. Normally arbitrage snaps it back. But the fix requires minting LUNA. And LUNA now flooding the market pushed LUNA's own price down. Falling LUNA meant the shock absorber was thinning. Which spooked more UST holders, who rushed to redeem, which minted more LUNA, which crashed LUNA further.
Every step of the self-correction was now a step of self-destruction. The machine designed to defend the peg was, under stress, the fastest possible way to destroy it. LUNA went from around $80 to fractions of a cent. Its supply exploded from hundreds of millions of tokens to trillions in days as the protocol frantically minted into a hole with no bottom. UST never recovered. Roughly $60 billion evaporated.
The code didn't malfunction. It ran perfectly. It did exactly what it was written to do — and what it was written to do, under a bank run, was dig faster the deeper it fell. A flawless implementation of a fatal design. The bug was in the whitepaper, not the software.
The line between honest and fragile stability
Here's the distinction worth carrying out of this:
Honest stability has a real counterweight you can inspect and, in the worst case, claim. A dollar. Overcollateralized crypto that gets liquidated to protect you. Something on the other pan of the scale that outweighs the coin. You can run to the exit and find something there.
Fragile stability has confidence, and calls confidence "reserves." It works beautifully in the demo and in the bull market, because in calm nobody tests the exit. Its true nature only shows the day everyone reaches for the door at once — and finds it opens onto air.
Algorithmic stablecoins with no real backing aren't stable coins that occasionally fail. They're bank runs with a delay built in, dressed as stability. The delay can be years. That's what makes them dangerous — the long calm reads as proof, right up until it isn't.
What you do with this
Not "avoid all stablecoins." A test you can run in thirty seconds:
- Ask what backs it. If the answer is "an algorithm" or "our other token," you're looking at Terra with a new logo. Weight, not faith.
- Ask where the yield comes from. If nobody can name a real borrower or real revenue, the yield is your own principal handed back to you on a schedule, and the schedule ends.
- Ask what's on the other side of redemption. Fiat-backed: a dollar (trust the custodian). Overcollateralized: seized crypto worth more than the coin. Algorithmic: whatever the market panic leaves, which is nothing.
- Assume the calm is not proof. Fragile systems look identical to sound ones — until the run. The absence of a crisis is not the presence of a cushion.
A stablecoin without a bank can be honest — DAI-style, overcollateralized, real weight in the open. What can't be honest is stability with nothing behind it. Feel for the counterweight before you trust the scale. When your hand closes on air, you've found the exit before the crowd does — and that head start is the whole edge.
Weight on the pan, or walk.