Here’s a humongous Hellmouth harvesting hardened humans! This 15th-century depiction of tortured souls was a common artistic motif and gets at the real fear that permiated Medieval society about what one’s place in the afterlife would be. Notably missing from the damned, here, were children.
And yet, folks did worry. The general view was that heaven was extremely difficult to enter; monks were in, usually, as well as martyrs for the Christian faith. But ordinary people were jeopardized by things like original sin and the idea that you cannot get into heaven if you have any sin that might mar your soul.
This led some to the grim conclusion that unbaptized children would end up in hell — the 5th century St Augustine and the 11th-century St Anselm thought this.
Child mortality rates being extremely high, however, made this line of thought upsetting to many. And so, in the 13th century, St Thomas Aquinas speculated that there might be an afterlife known as limbo, from the Latin “limbus” which means “edge”, as in “at the edge of heaven”. There, he reasoned, unbaptized children could exist in a sort of happiness that fell short of full-heaven bliss.
Today the Catholic Church no longer teaches that limbo is a thing, chucking it from the catechism in 2007 (in fact, it had never been the official doctrine, but was widely taught).
Sources: Miniature 1540 Hours of Catherine of Cleves, public domain, errata 1440. Review _Children of the Middle Ages_ Nicholas Orme, _The Virginia Quarterly Review_, vol 78 no 4 (Autumn 2002), pp 766-773. @Religious Tolerance, “limbo,” Dec 19 1999, B.A. Robinson.