Spell: Glyph of Warming: When you cast this spell, you inscribe a glyph that warms items or other
creatures, either upon a surface (such as a table or a section of floor
or wall) or within an object that can be closed (such as a book, a
scroll, or a Treasure
chest) to conceal the glyph. If you choose a surface, the glyph can
cover an area of the surface no larger than 10 feet in diameter. If you
choose an object, that object must remain in its place, if the object is
moved more than 10 feet from where you cast this spell, the glyph is
broken and the spell ends without being triggered.

The glyph is nearly Invisible and requires a successful Intelligence (Investigation) check against your spell save DC to be found.

You
decide what triggers the glyph when you cast the spell. For glyphs
inscribed on a surface, the most typical triggers include touching or
standing on the glyph, removing another object covering the glyph,
approaching within a certain distance of the glyph, or manipulating the
object on which the glyph is inscribed. For glyphs inscribed within an
object, the most Common
triggers include opening that object, approaching within a certain
distance of the object, or seeing or reading the glyph. Once a glyph is
triggered, this spell ends.

So yeah, a magical glyph that produces a pleasant warmth, great for reheating leftovers or warming up after going out adventuring when it’s a bit nipply out.