Octashroom is one of the five skins released in The Fungus Amongus Planet event. It could be purchased in the item deal part of that event in late January 2023.
Octashroom could be purchased for $3.99 in a limited time deal which included packages of 6500 coins, 300 DNA and 1000 mushrooms. It was not available for individual purchase and may not be available for purchase in the future.
Details of this skin may vary depending on location, platform or time.
Note: Octashroom was released again in the July 2023 opening of The Fungus Amongus Planet event. This time Octashroom could be purchased in a different item deal for $5.99. This limited time item deal included the Kaiju Shroom skin, 1700 mushrooms, 10000 coins and 800 DNA.