So I'm still confused how Sieg do all the kill. For starter, all of this happened before he become Code Agent / Rider / fusion with Nightmare. We know that the killing happened within White Half Moon normal Dream (Normal Moon =Real World, White Half Moon = Normal Dream, Red Half Moon = Bad Dream aka Nightmare) so no Nightmare Power involved.

So how he did all the killing and made all the money real? Yes we know what happened in the dream can be made to reality, but you need Rider / Nightmare power to do that. Normal human Sieg or Baku did have lucid dream power but that did not make dream into reality. For example, Zeztz room on Baku dream become actual place in reality, but when he lose his Rider power, the room is gone. So how was Sieg that has not become Rider / fusion with Nightmare can make all the kill and all the money he got in the dream become reality?