This would make sense if the formatting of the ability matched every other ability. It doesn't. Instead the ability has bold text (like all other mutations) but is phrased like a monster ability (which never has bold text).

I ruled that it would be a once per rest ability when a player got it as a mutation. The players cannot get any sand from the squid's puppet as it is already dead. The ability itself is a double edged sword as no one can see through it. This struck me as a reasonable compromise.

The monster sounds like a cool idea, but its text is definitely wrong.