That's pretty awesome. It more than does justice to the wickedness of Malzahar.
I'd like to try and find specific things to say about this, but it's actually kind of hard. The color scheme feels very right here, fitting of both the mystery and the malice of the Void, its denizens, and those who have been touched by it. The effect of both Malz and his voidling coming from out of the shadows and being illuminated solely by the warped, violet light of the void magic he's conjuring in his right hand is a very nice touch, as is the eerie glow of their eyes. You managed to give the piece a textured look, too. It makes me think I could almost feel the cloth of Malzahar's clothes or the hard bumps and cracks on the voidling's chitin.
Like I said at the top, it more than does justice to Malzahar. If it hasn't been included in a Summoner Showcase yet I urge you to submit it.