Soul Speed enchantment should also work on skulk/skulk-related blocks

In keeping with the 'Soul' motif we have seen in the Minecraft Live coverage of the Deep Dark, as well as the visual design of the Skulk Catalyst particle effects and the Warden, I feel it would be appropriate for the Soul Speed enchantment to work on skulk-related blocks.

This could have the practical effect of allowing you to move faster whilst sneaking over these blocks, or (if that should prove inconvenient for building purposes etc.), it could prevent you from making footstep noises whilst walking normally on skulk blocks and skulk growth. Considering that this 'silencing' effect will not apply to regular stone blocks in the vicinity of the skulk, it is not a warden cure-all — rather, a precaution the well-prepared adventurer might take to help slightly improve their chances of survival whilst navigating or escaping the ancient cities.

Given that Soul Speed only has fairly niche applications, I feel that this gives the enchantment a touch of renewed purpose, without compromising the challenge of the Deep Dark. Furthermore, as a treasure enchantment, it has an added level of accomplishment; you, the player, have quested to the Nether, and returned with a magical item that *might* just save your life in the ancient depths of the world — but heaven forbid if your boots break at the eleventh hour.