While magical summons and banishing spells are powerful tools, they are not
without remedy. One such remedy is the anti-summons spell called heavy weight.
This spell binds the target with magics that prevent summons. This magic is
strong enough that the target will not be able to cast most summon spells
himself. Sometimes the magic can be defeated as it is not 100%, but currently
this is the only anti-summoning spell that is well known. There are rumors
that somewhere there are scholars who even now, try to find the right
incantations to improve this spell, just recently there has been a discovery
of a spell that will remove heavy weight before it wears off. . .