This is a KubeJS addon that allows for script creators to have access to creating custom Iron's Spells and Spellbooks features, such as:

• Custom spells
• Custom spell schools and attributes for them
• Custom special items such as staves, spell books, and magic swords
• Special event handlers, e.g. PlayerEvents.changeMana
• EntityJS compatibility for custom spell-casting mobs and changing existing mob AI to cast spells
• Alchemist Cauldron recipe support
• Full ProbeJS support
• More soon!

More info on the official KubeJS Wiki page for third-party addons.