Union Attack (Mosaic Rare) (BP02-EN152) - Battle Pack 2: War of the Giants Unlimited

Target 1 face-up monster you control; add up the total ATK of all other face-up Attack Position monsters you currently control, then during the Battle Phase of this turn only, the monster gains that much ATK, but cannot inflict Battle Damage to your opponent, also other face-up Attack Position monsters cannot attack.