Hoarfrost and Pyroclast both lack the special "opening portal" effect when being summoned, which was a departure from a previously established pattern from Zuqoth and Aderene. I figured that we'd see this effect again with Siluruz, but it's also missing. Keeping in mind that the crow assistants have their own unique portal effect when they're summoned.
It's a minor complaint, admittedly insignificant, but I was a little bummed out that not all my Daedric assistants share a theatrical flair.