Analyze Portal

You can tell whether an area contains a magic portal. If you study an area for 1 round, you know the sizes and locations of any portals in the area. Once you find a portal, you can study it. (If you find more than one portal, you can only study one at a time.)

Each round you study a portal, you can discover one property of the portal, in this order:

• Any key or command word needed to activate the portal
• Any special circumstances governing the portal's use (such as specific times when it can be activated)
• Whether the portal is one-way or two way
• Any of the usual properties described in Magic Portals
• Finally, a glimpse of the area where the portal leads. You can look at the area where the portal leads for 1 round; the range of the caster's vision is the spell's range. Analyze Portal does not allow other divination spells or spell-like abilities to extend through the portal. 

For each property, you make a caster level check (1d20+caster level) against DC17. On a fail, you can try again the next realm.

Analyze Portal has only a limited ability to reveal unusual properties, as follows:

• Random Portals: The spell reveals only that the portal is random and whether it can be activated now. It does not reveal when the portal starts or stops functioning.
• Variable Portals: The spell reveals only that the portal is variable. If the caster studies the portal's destination, the spell reveals on the destination to which the portal is currently set.
• Creature-Only Portals: The spell reveals this property. If the caster studies the portal's destination, the spell reveals where the portal sends creatures. If it is the kind of portal that sends creatures one place and their equipment another place, the spell does not reveal where the equipment goes.
• Malfunctioning Portals: The spell reveals only that the portal is malfunctioning, not what sort of malfunction the portal produces.

(From Manual of the Planes, 3.5e)