Bon la solution (en anglais parce que j'ai la flemme de traduire :
Trade mal'ganis and one 3/5 voidwalker into one of their 5/11 voidlords. Mal'ganis survives as a 9/2
Trade your second 3/5 voidwalker into one of the opponent's 3/5 voidwalkers. This leaves a 3/2 voidwalker on their side (and yours)
Trade your 5/6 voidcaller into their second 5/11 voidlord, leaving a 5/6 voidlord on their side and a 5/1 voidcaller on your side
Cube mal'ganis
Trade your (now) 3/1 voidlord into their 5/6 voidlord to leave a 5/3 voidlord on their side and a 1/3 voidwalker on your side
Defile. 1-health = your voidcaller, 2-health = their 3/2 voidwalker, 3-health = your voidwalker, 4-health = their 7/4 doomguard, 5-health = one of their 3/5 voidwalkers, 6-health = your cube
At this point you summon two 11/9 mal'ganises. The +4/+4 buffs your remaining doomguard (from 5/1 to 9/5) and voidlord (from 3/3 to 7/7)
7-health = their mal'ganis, 8-health = their last spawned 3/5 voidwalkers (which become 1/1 after the opposing mal'ganis dies). At 9-health the defile ends. Your mal'ganises live as 11/6s
Swing face with your surviving 9/2 doomguard and 7/4 voidlord. Hero power face for 3. Exact lethal (19).