Rust Belt

Instant -

a cog you control, destroy this: Gain

.

Battleworn

Rulings

From the High Seas release notes · June 6 2025

Rust Belt’s activated ability will still resolve even if the cog you control that you tapped to pay its activation cost is destroyed before the activated ability resolves on the stack.

Keyword notes

Battleworn - Equipment that wear down after each time they are used to defend. If you defend with a card with Battleworn, put a -1{d} counter on it when the combat chain closes.

When you defend with a card it remains on the combat chain until the chain closes, therefore you cannot defend with an equipment multiple times on the same combat chain.
A -1 counter stays on the card until the card is destroyed or the game ends.
If the defense of a card that is defending is below zero, its defense value is considered to be zero.
When this card is destroyed, it is sent to your graveyard. (Not when it has 0)
When this card is destroyed, it is sent to your graveyard.
If the defense of a card that is defending is below zero, calculate as if its defense is zero.