Glyphs
by Paul George DooleyGlyph of Warding has it's limitations, perhaps there are other types out there.
Such as:
Glyph of Healing. A glyph which allows curative magic to be placed on
walls. As the wounded defenders of the castle fall back they get healed.
Glyph of Dispelling. A harmful effect as it potentially strips the
invader of precast spells so may not require a separate spell.
Glyph of Protection. Can cast a defensive magic e.g. Bless, Aid,
Protection from Fire, Remove Fear etc.
Glyph of Magery: Activates a non-damaging mage spell such as Web or
Wizard Lock
Perhaps there is a spell (Glyph of Activation?) out there already , which allows such things.
Imagine trying to take a castle which had been defended with such magic.