Shadow slice actually works with illusions since it doesn't say 'target creature'. You can cipher on a illusion.

Remove somnophore, jace's phantasm, jace's mindseeker, hover barrier - you have no way to make them work.

• 2 phantasmal bear
• 2 Krovikan mist
• 4 Delver of Secrets  ^Flip

all of your black is pretty suboptimal, but this is casual, you decide how far to take it. What I suggested is what I feel is the more consistent build

Grand Architect , Phyrexian Metamorph , Wurmcoil Engine , Counterspell , Dismember , Into the Roil , Mana Leak and Summoner's Bane could help.

Thank you for suggestions, I made some changes. Although, the art-whore I am especially for a casual deck I wanted to keep the hover barriers :p And somnophores just for random laughs of keeping enemy board tapped. Didn't want to add other creatures than illusions either. And good point on the shadow slice, never figured out it doesn't say target.