From Hard Drop - Tetris Wiki

Shadow Cannon is a set of continuations found by westl from the first bag of Gull Wing TSD. The dependencies are I before Z and L before S, or if mirrored I before S and J before Z. It can be used as an Anti-Perfect Clear opener due to the fact that the first TSD can be built quickly, or simply an opener that sends a quick attack at the very start of the game, like Stickspin.

First Bag

First Bag

Residue

Setup rates are 43.33% on one side, or 57.22% when counting both orientations. This resembles the first bag of a TKI 3 Opening, except for the fact that the S/Z piece is placed vertically.

Second Bag and Later

S -> OL, I -> J

This has many dependencies in the first bag but is fairly reliable after that. Notably, this path stacks high and does not send much at the start, so it may be a riskier choice.

Second Bag

Residue

Third Bag

Third Bag

Residue

This can be stacked most of the time. It will fail if S and T come before both L and J. If this happens, you can either sometimes place only the I and Z before making the TSD, or skim by placing the T piece before the TSD is completed.

Fourth Bag J -> O

Fourth Bag O -> J

The fourth bag can be stacked in one of two ways. Note that only S and Z need to be placed for the T-Spin Triple to be complete.