Jarrall + Merchant is the ideal starting hand. The goal is to ramp to 7PPP and drop
Jarrall Iceheart +
Savagery and use the overwhelm from killer to trigger Jarrall's infiltrate ability, which can only hit on Decimate. After a heinous sound, Jarrall will then do 10 overwhelm damage to every enemy unit still on the board.
The extra mulligan is pretty handy for 50 power combo decks.
Edit1: From AetherLlama's version (
Savage Jarrall OTK), the value gained from increased OTK potential of
The Witching Hour is greater than the potential followup cast of Decimate after drawing. Also fits the theme of the deck better.