I played a couple of rounds and I think you are cooking something interesting.

Some toughts:

• For me the strong part are the enemies and their round defining abilities
• Player ability part is weaker for me (but admittedly, once someone remembers what abilities do, it probably become easy)
• Maybe there is something like this later, but some sort of quick time event things happening on the tetris board could work here (something unexpected falling down, or an ability being tiggered like a note from guitar hero), may be better than the current abilities (my eyes are on the board, I cannot loose focus and look at my ability counters)
• Strong visual effects when the enemy messes around with your blocks would go a long way for readablility

lot's of progress since last time. lot of cool ideas of messing with the player in this. some are kinda op though imo like the one that shifts an entire horizontal line at random or the double-blocks one. i feel like getting 7 lines against those enemies is kind of a tall ask, but then again there are items to mitigate that i guess. 

while fighting a missingno the game crashed though.

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ERROR in action number 1

of Draw Event for object obj_tetromino:

local variable _ghostPiece(100480) not set before reading it.

at gml_Object_obj_tetromino_Draw_0

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gml_Object_obj_tetromino_Draw_0 (line -1)