when it is destroyed does it lower DS by 1?

Rogue 3 said:

Read the Interupt description in the rulebook. Then see if you still need an answer.

I'm not saying that to be a jerk, but it's going to be a core game concept that you need to understand, so I think it's important you take a second look in the rulebook.

i mainly ask cause on octgn it does. im 99.9% sure it doesnt.

Note that it's ability is an interrupt, which means that it resolves before the triggering condition. That is why it can trigger on its own death:

- The objective is about to be destroyed

- The interrupt triggers and resolves, lowering the DS dial by 1

- The objective is destroyed

dbmeboy said:

that what i assume as well but just to play devils advocate-

the card states "When an objective you control leaves play"

wouldnt it have to actually leave play before you can activate the interrupt?

And once it leaves play there is no interrupt to use since card is not on table.

I understand why you would think that, but that's not how the timing rules in this game work. Interrupts will always resolve before the triggering condition happens. For other examples, see some of the units that have interrupts to themselves leaving play (Leia and X-Wing Escort off the top of my head).

Rogue 3 said:

This is why I said a reading of the rulebook may do you good for this question.

"Interrupt abilities are clearly labelled by the word
“Interrupt” followed by effect text. Unlike actions, which
are resolved during action windows, interrupts may
be executed when the specified triggering condition
occurs, as described in the interrupt’s effect text.
For example, a triggering condition could be “when a
player draws a card…”
It is possible for multiple interrupts (and reaction
abilities) to be executed from the same triggering
condition. Always resolve interrupts to a triggering
condition before resolving the effects of the triggering
condition itself.
The active player has the opportunity to resolve the
first interrupt to a triggering condition, followed by his
opponent. In this way, players execute one interrupt at a
time until both players consecutively pass. Resolve each
interrupt completely before the next is executed.
An interrupt effect is considered to be resolved before
the triggering condition is allowed to complete -- often
cancelling or changing the outcome of the triggering
condition.
A card’s interrupt effect may only be
resolved once per triggering condition.
“Lightsaber Deflection” is an example
of an event card with an interrupt
effect. In this case, it may
be played when a friendly non-Vehicle
unit is dealt damage."

To break it down in steps:

1. Decoy at Dantooine is destroyed.

2. When it leaves play (i.e. before it goes to the DS player's scoring area, as per "when" conditions from the interrupt rules), it lowers the DS dial by 1, to a minimum of 1.

3. Decoy enters DS player scoring area.

4. LS objectives in DS scoring area are counted.

5. DS dial goes up appropriate number.