The magnacarta established foundation of what would become

The English Parliament.

Explanation:

The Magna Carta, signed on June 15, 1215 by King John I of England, was the first event by which a limit was placed on the full authority of the English monarchy. Thus, a series of rights were established for the feudal lords and barons of England, while limiting the authority of the kings by forcing them to respect the rights of the nobility.

This document and its principle of limited government was the fundamental basis for the creation of Parliament, as an institutional body that, based on the principles of the Magna Carta, served as a counterweight to the powers of the monarchy.