Thought Devourer

• WWizards of the Coast2009-10-01
  Official Ruling
  If multiple effects modify your hand size, apply them in timestamp order. For example, if you are affected by Cursed Rack (an artifact that sets a player's maximum hand size to four) and then put Thought Devourer onto the battlefield, your maximum hand size would be zero. However, if those permanents entered in the opposite order, your maximum hand size would be four.

Rulings via Scryfall