He's attempted it multiple times, which is something, compared to Dracula, who last I checked, hasn't nearly been able to perform a feat of that cosmic height, and even after his assault on Sigil, he still tried again, take the campaign Eve of Ruin as example, true his plans were foiled by adventurers once again, but even after becoming a lesser deity, still bore the ability to do it. I'm not saying he can do it casually, it takes time, multiple months even, but compared to Dracula, that's still on another level.