From ErfWiki

Magic 101
Natural Magic, Caster, Caster link, Juice, Scroll, Magic Item, Spell, Grandiocosmic Strings, Nodes

Proposed Canon

Grandiocosmic Strings or G-Strings are the conduits of all magic power in Erfworld. Only Thinkamancers know of their existance. The majority of (if not all) Thinkamancy Spells are actually the Thinkamancer manipulating the G-Strings of the other Units.