This turn, each of your attacking units in the Space arena gets +X power, where X is the amount of Shields that unit has, and each of your defending units in the Space arena loses Shields.until end of turn.
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.