Lu Huaining transmigrates to the early years of the Great Tang.
At death's door, he discovers that he has somehow brought along a pocket dimension. Determined to make a name for himself, he sets out on a journey of revenge and plunder.
He rises to prominence overseas, until a mysterious group appears.
As Lu Huaining's identity is gradually revealed, he takes on a new role and leads the Great Tang to its peak.
[Alternate history + pocket dimension + development + struggle for supremacy] The story focuses on overseas expansion. If that's not your thing, don't read.
Very good book