Dropping to 0 HP does not cause unconsciousness or death saves.
You gain a level of Exhaustion Nimble and the Dying condition.

Dying condition

Limited actions:

Your AP is limited to 1 per round,Concentration Nimble is broken and cannot be maintained.

Risk of Further Injury

Continuing to fight mai further harm you:

• Attacking or casting spells require a DC 12 STR save, gaining 1 level of Exhaustion Nimble on a failed save
• Taking damage while Dying causes 2 levels of Exhaustion Nimble
• Taking a critical hit while Dying causes 3 levels of Exhaustion Nimble