Sometimes a spell in the PHB or other source will have the name of some ancient wizard from another world involved. None of those names are valid on Wyrlde. Spells here are not named after the person who creates or popularizes them – they are descriptive of the action.
All Mages (Sorcerers, Warlocks, and Wizards) inadvertently create a magic circle around them when they cast a spell. These circles take many different forms – from floating, unreadable script that circles around them, to a small circle around the focal point of a spell, to a large scale circle that spread out beneath them or beneath the target of their spell.
They always glow brightly – they can change a pitch black room into dim light – but they are always there and always visible. This circle is unique to each caster, and they can be simple or complex, but no two are alike among any living or undead mages – but there have been cases where after the death of a Mage, another mage has come into their power with the same circle.
It is said this was done by Pallor, Dusit, Mystren, and Shavan working together, but it may also have been a tweak to the world by Antelle or Paria. Hard to say.
It is permissible to use spells from other sources that are official and published, provided that the player using those spells has the sourcebook in their possession.