(Anyway, moving back to the current situation...)
As soon as Deathbringer starts shouting, Dr. Madness tosses the cape he was holding into the air above himself. As the cape floats down over Dr. Madness, it appears to be enveloping him just like a portable hole would. Dr. Madness stage whispers "Be warned, not everything here is as it seems.", leaving a sort-of audible echo of that statement as the cape folds in upon itself, popping out of this plane of existence and into Hammerspace itself.
"He's forced me to recede into Hammerspace. Hmm... poor choice on his part...", Dr. Madness mutters to himself as he wanders about, looking around. He's turned Hammerspace into his personal storeroom, containing all his scientific and pseudo-scientific ("mad science") projects, as well as the typical arsenal of blunt objects. "Now, what to use, what to use..."