Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Tower-Defense Toolkit 3 (TDTK-3) Free.
Tower-Defense Toolkit v3.1.1.f3
DISCLAIMER: This is an older version of TDTK that has been discontinued. It doesn’t work on Unity2018.3 or later. If you are interested in the latest version, please see the one in this link instead.
Official Website – Link
Unity Support Forum – Link
Quick Video Overview – Link
WebDemo – Link * this is a demo for the new version of TDTK
TDTK is a C# coding framework for the easy construction of TD games of any kind. It comes with a bundle of scripts that are flexible and configurable to fit a variety of TD gameplay scenarios. It’s mobile compatible.
The toolkit is designed to be used with custom models and art assets. You can easily integrate your own art assets to make your unique TD game.