This (-た)もの refers to a resultant product, i.e., something obtained by performing the preceding verb. In your sentence, もの refers to the product made by remaking, i.e., the remake version.
This is a very common and useful pattern in Japanese, but it's often hard to translate it directly using "(some)thing" into English...
- スパゲティとは小麦粉を細長い形にしてゆでたものです。
Spaghetti is food made from flour shaped into long pieces and boiled.
- コーヒーからカフェインを抜いたものはデカフと呼ばれる。
Coffee with caffeine removed is called decaf.
- 彼女は狐が姿を変えたものだ。
She is a fox in disguise.
- この絵は有名な画家がクレヨンを用いたものだ。
This painting was drawn by a famous artist using crayons.
- 真改とは薄桜鬼の第一作を「薄桜鬼 真改」としてリメイクしたものです。
"Shin Kai" refers to Hakuōki Shin Kai, the remake of the first Hakuōki.
(More literally: "Shink Kai" is something we made by remaking the first Hakuōki as Hakuōki Shin Kai.)