on a really cold night in canoe country I heated up a good size rock and rolled it into the vestibule of my tent to warm it up.
it took the edge off the cold but the rock,a big one,seemed to cool off fairly fast.
a army poncho liner was another bit of gear I take along and it
does act as a extra blanket but slips off after a bit.
a Gaz lamp really heats up a tent as I found out when I was reading half way out of the bag in a tee shirt.
when it's lights out and cold I put on everything plus a watch cap.
camping next to lakes makes for a damp camp and that's sometimes
as bad as cold.