the character is from the game Medieval Total War II and uses its skeleton and some corresponding animations, converted to Milkshape format ms3d. it can be imported to Esenthel, but previously I modified the animations in Fragmotion to be game engine compatible (mocap animations have moving pelvis, in game engines it should stay around origo).
the game model packs can be unpacked by an official tool, and they also released all animations for the modding community some years ago. I use them as placeholders. but their previous game Rome Total War is also moddable, there are a lot of tools for it. I collect many experience from game modding! earlier I used for my tests a vertex animated model converted from Age of Mythology, which is also moddable.

there is a default skeleton in Esenthel, if you apply it for your human character model after importing, you can use the default animations. I did not tested it but there is a tutorial video as I remember showing how to assign vertices to bones and how to set their weighting...

and yes Esenthel requires good C++ programming knowledge, so I stay with 3DGS to finish my developments and make my first real game, beside getting experience in Esenthel too, which has some benefits in some categories.