C0rtana

I thought of adding both of those, but: With Shadow Sliver, I cannot block enemy creatures anymore, Shifting Sliver makes me able to attack without being blocked and still be able to block if needed. And I haven't seen a sliver with infect, only with poison 1, and I thought that it's better to have a 4/4 unblockable sliver deal 4 damage than exactly 1 poison damage.
And thanks for the idea to mov Overlord to the sideboard, did so now!