Neither of you sees the other's deck until the game starts.
Battle pack quick match
Both sides open a random Arena battle pack — 25 cards, a hero and
his own ten, plus thirteen off the sheet and a rare — and however
many 11-card boosters you agree on. You play what you open: no 40-card
minimum and no 3-copy limit.
Your games
Discord notifications
Enable Developer Mode in Discord (Settings → Advanced), right-click
your name, Copy User ID. Without it you are named but not pinged.