Missing cards are 2x Reverberations. The site does not seem to want to load those at the moment.

The idea is to build up Sif to 4 or 5 spell damage, and on turn 8 play Magister's Apprentice - Sif- Arcane Bolts!

Alternatively, you can wait for 11 mana (thanks to Audio Amplifier) and play Reverberations on Sif to double the spell damage.

You can probably improve this deck by replacing the secret package with an elemental package, but where's the fun in that :)