Are we to think of the tentacle as a coiled up spiritual weapon with reach which covers a 10 ft radius around a point, or is it like a 10 ft line, which can attack anything within 10 ft of this 10 ft line, making its covered area a 20 ft x 30 ft rectangle (or possibly 25 ft x 30 ft if on a grid) ?
I realize it doesn't occupy space, but it does say it's 10 ft long and can hit anything within 10 ft of it. Logically, we could assume the tentacle has one orientation, and it can only strike from a point 10 ft from its base. But a more literal reading of the feature might imply otherwise.
Is the attackable area a circle or a rectangle?