To edit UTX files, use L2Editor and encdec.
Here's some documentation. UDN - Two - UnrealEdInterface (unrealengine.com)
To edit an utx file, simply go to the texture browser, click file > open, open the desired file, click on file > import to import your textures, then simply save the .utx. After that you need to encrypt the .utx file by dragging it over MXC EncDec (in L2Editor's folder) and simply put it on your Systextures. Or otherwise, you can change the file extension of the .utx to .u and put it on your system, to avoid encrypting it.
It's better to create a new .u file, no need to recompile LineageMonster from scratch; that said your 'LineageWarrior.u' is missing a class called 'LineageRidePawn'.
add this file to your compiler's system and try again
LineageWarrior.u
also, here's a nice guide in case you haven't checked it out yet
911reg's post in Texture modify H5 was marked as the answer