Grim Grotto is a mid-game prophecy trimming setup that yields a T-Spin Triple. The order of the hang or trim are interchangeable.

Grim Grotto

The easiest way to remember is to look for the square shape (outlined). Make sure one uses the right piece though. If they use the wrong S or Z, it will create an "empty" S or Z-Spin Triple instead.

• Compulsory: One must be careful of using the wrong piece.

Grim Triple Double

This is a greedier Grim Grotto (credits to XaeL):