Sealed by Miquella?

[River Victor]

I found the hole that you can drop down to its depth and found a fog gate, but it is sealed by Miquella. What do I do to open it?

[echo_ML]

Enter the big spooky black castle and it breaks.

[River Victor]

Originally posted by echo_ML:

Enter the big spooky black castle and it breaks.

Shadow Castle? I've killed Messmer. Is that it?