Cycles (or Blender in general? or all imaging softwares? ) is bad at stacked transparencies, first. Your converted sage will be time consuming to render.
Conversion is possible - there was even some addon for that iirc, however this is fairly easy to do manually and addon wont give you material you could come up on your own.
Second, images in file are not by any means optimized for rendering on a pc - all sizes are random numbers which are not “power of two” rule being used in binary world.
Third - while some of included in blend file images (actually all which are really used) are png, available alpha channel is not used to create transparency, instead, separate texture image is used which feels odd, not efficient and makes asset mess.
Considering all this here’s a sample of material and how sage does look rendered in cycles.
Conversion is easy - you need 3dview, UVeditor and Node editor open, Blender render initially. Switch to Cycles render and with some plane selected on Node editor menu tick and un-tick Use Nodes. This will create Output and Diffuse nodes. Now, when back in Blender render, check which images are used on Texture tab. If you click on texture slot selected image will be shown in UV editor - take image icon near the image name on UVeditor status line and drag into Node editor - this will create Image Texture node with already selected image in it. Connect as desired.
Nodes in blue are actual material; red - original images, green - combined and resized image, 128x512.