If Quicksilver, Brash Blur is in your opening hand, you may begin the game with him on the battlefield.
Haste
Power-up — : Put a +1/+1 counter and a double strike counter on Quicksilver. (Activate each power-up ability only once. Reduce the cost by his mana cost if he entered this turn.)
A one-time activated ability found on permanents that costs less during the turn the permanent with the ability entered the battlefield. See rule 702.193, “Power-up.”