Pentagram

Special; Resists attempts to cross it 
Produces a magical barrier, which blocks hostile spells and magical creatures from passing in either direction. The barrier is a star-shaped figure drawn on the floor or ground. Magical creatures (demons, golems, creations, zombies, elementals, and the like) cannot cross the border of a pentagram; neither may they cast spells, or move any physical object, across the border. 
Nonmagical creatures – including mages – can freely cross a pentagram, though they cannot cast spells across its border. Spells of transport (e.g., Flight, Teleport) cannot be used to enter a pentagram for hostile purposes. 
Certain very hostile creatures may be summoned within a pentagram; the caster stands outside and summons the creature to a spot inside the pentagram. The caster will open the pentagram only when he is sure he can control the summoned creature. Magical creatures (demons, golems,  
creations, zombies, elementals, and the like) cannot cross the border of a pentagram;  neither may they cast spells, or move any physical object, across the border.  
If part of the pentagram is cut or erased, its power will be lost until the caster can rejoin the pentagram – all this requires is a piece of chalk and time (usually just a second) to draw the line. No magic spell can injure the pentagram, but physical attacks – like walking up and scuffing out a line with your shoe – can succeed if they are made by nonmagical beings. A demon or creation could not do it; an ordinary person could. Likewise, an ordinary person could throw a rock into a pentagram, but a demon or golem could not. 
A magical creature may try to force its way through a pentagram. Roll a contest between the creature’s (ST+Will)/2 and the skill with which the pentagram was cast. If the creature wins, it destroys the pentagram! No one creature can thus “test” a pentagram more than once per day.

Duration: Permanent unless broken. 
Cost: 1 per square foot protected (minimum 10). When the spell is cast ceremonially, the casters can spend extra energy to increase the effective skill of the Pentagram. A mage can also use the Slow and Sure Enchantment method (though Pentagram is not technically an Enchantment spell) to create  a large pentagram by himself. 
Time to cast: One second per square foot. This time is spent in tracing the line, and is necessary no matter how well the spell is known or how much power is available. 
Prerequisite: Spell Shield.

Item 
Mages’ Guilds may have permanent pentagrams, inlaid with tile or jewels to avoid accidental scuffing, and cast at a very high level of skill. 
Such a design can be ritually “cut,” when necessary, by a chalk-mark. But there is no intrinsic difference between these and a regular pentagram – any pentagram is “permanent” until erased or broken. (If a hostile creature breaks through a Pentagram spell, it destroys the enchantment but does not affect the physical design, which can be re-enchanted later . . . if its owner survives.)