Weaver Worms

At the beginning of your end step, if you control four or more untapped lands, create a white 1/4 Silkworm creature token with "Whenever this creature becomes blocked, tap all creatures blocking it. They dont untap during their controllers next untap step."
Giant silkworms furrow these ice sheets, leaving behind great roads of magical thread. As well as being incredibly strong, the silks can be woven into fabulous fabrics.