Austere Command instructions not performed in correct order.

[Tharkon]

Austere Command instructions not performed in correct order.

[github-actions]

Austere Command - (Gatherer) (Scryfall) (EDHREC)

{4}{W}{W}
Sorcery
Choose two —
• Destroy all artifacts.
• Destroy all enchantments.
• Destroy all creatures with mana value 3 or less.
• Destroy all creatures with mana value 4 or greater.

Oubliette - (Gatherer) (Scryfall) (EDHREC)

{1}{B}{B}
Enchantment
When Oubliette enters the battlefield, target creature phases out until Oubliette leaves the battlefield. Tap that creature as it phases in this way. (Auras and Equipment phase out with it. While permanents are phased out, they're treated as though they don't exist.)

Serra Ascendant - (Gatherer) (Scryfall) (EDHREC)

{W}
Creature — Human Monk
1/1
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
As long as you have 30 or more life, Serra Ascendant gets +5/+5 and has flying.

[Tharkon]

Additionally a [[Callaphe, Beloved of the Seas]] was enchanted by [[Screams from Within]]. When the creature died, Screams from Within triggered even though it should not be on the battlefield anymore.

[github-actions]

Unable to retrieve information for "Callaphe, Beloved of the Seas"

Screams from Within - (Gatherer) (Scryfall) (EDHREC)

{1}{B}{B}
Enchantment — Aura
Enchant creature
Enchanted creature gets -1/-1.
When enchanted creature dies, return Screams from Within from your graveyard to the battlefield.

[JayDi85]

Related rules about modes order resolve:

Each of the chosen modes happens sequentially. If a permanent has an ability that triggers whenever it or another permanent is destroyed, it will see permanents destroyed at the same time as it or before it, but not permanents destroyed by later modes.
(2020-11-10)

If the first and last modes are chosen, an artifact creature with mana value 4 or greater will have to be regenerated twice to survive. This is because the modes happen sequentially, and the regeneration "shield" is used up by the first one. The same is true with any other combination of modes that covers one permanent twice.
(2020-11-10)