Chaos Rune

Item: A simple or martial weapon
A popular project among apprentice artificers,
this rune embodies the chaos of unbound magic.
When you score a critical hit with an attack using
this weapon, roll on the Wild Magic Surge table
in the Player's Handbook to create a magical effect.
If the effect is a spell that requires concentration,
it doesn't require concentration in this case and
lasts for its full duration.