It is similar to Skeletron, but smaller and less powerful.
It will spawn about once every night.
it can also spawn more than one time a night plus it can be hard to defeat because of the zombies swarming you
Before a skulliton appears the message "Look, a Terrarian, let's play with him/her." will appear. This is similar to the mechanical boss messages when they spawn on their own.
When the night ends, and you haven't defeated Skulliton yet, a message appears: "Daddy said to get back by morning, goodbye."
When killed the remains of Skulliton are as large as Skeletron's