Search your deck for a Grand Admiral Thrawn unit card, show it to your opponent, and put it into your build zone with 1 build counter on it. Shuffle your deck. Play only during your build step.
Keywords
Shields
Shields X: A cumulative, static ability that means, "The attacking unit gets –X power against this unit." Shields only matters when attack dice are rolled. If you give a unit Shields after your opponent has rolled for damage, it doesn't affect the roll.