Wizard Lock: Similar to a Hold Portal, this spell lasts indefinitely. It can be opened by a Knock without breaking the spell. A Wizard Lock can be passed through without a spell of any kind by a Magic-User three levels above the one who placed the spell.There are a couple common features of these two spells:
Continual Light: This spell creates a light wherever the caster desires. It sheds a circle of illumination 24" in diameter, but does not equal full daylight. It continues to shed light until dispelled. Range: 12".
- They are upgrades to lower-level spells, but the the upgrade is extreme: duration goes from a limited number of turns to indefinite duration. Significant because later editions or alternative spell systems like Spell Law introduce many more grades between "short" and "infinite".
- There's a physical change, but not necessarily a physical force. Contrast both to Levitation.
There's no range listed for Wizard Lock, but it should probably be short, maybe 20 feet. Continual Light, on the other hand, has a range that notably is equal to the radius of illumination; you could perhaps redefine it as "the caster must be in or touching the area to be illuminated."
Continual Light again doesn't mention a mobile light source. Also notable is that, if neither Light nor Continual Light cause an item or point in the air to emit light, but cause an entire circle to be illuminated, then the light cannot be blocked, unless the entire illuminated area is enclosed. If a caster places the spell on an object, I think I would rule that Continual Light "shuts off" permanently when the object is moved; otherwise, the area stays illuminated until countered by Darkness, Dispel Magic, or a powerful demon or anti-magical creature. The illumination would not be visible outdoors during the day (not as bright as full daylight.
There's been occasional discussion of whether Continual Light breaks a setting meant to be more medieval in feel. If Continual Light exists, the argument goes, then cities would hire squads of magicians to create free, permanent streetlamps. Assuming that there really are plenty of magicians for hire, magic is practiced openly as a trade, and Continual Light spells are easy to come by for those seeking to learn it, then we actually get into the same problem as in modern-day cities: some people (particularly criminals) won't want Continual Light and will find ways to "shoot out the lights" to provide cover of darkness for their activities. Thieves who don't have Darkness scrolls will hire magicians who can cast Dispel Magic. The city government will have to pay to have the spells recast, and the other side will dispel them again, and so on. End result: spotty illumination, if any, and lots of wealthy magicians.
That's assuming cheap, common magic. By the book, however, it costs 20,000 gp to research Continual Light with guaranteed success. An M-U who reaches 3rd level entirely by finding treasure and never has to kill a monster will amass 5,000 gp, 500 of which must be spent on upkeep. Even if you assume there is easy access to magic, individual spells might be very rare, and magicians most likely would horde their spells because of the substantial investment required just to get a single spell. Magicians who agree to provide magical service would try to make the spell pay for itself, dividing the cost of spell research by the number of times they expect to cast the spell; Continual Light, being a permanent spell and thus not a source of repeat business (except in the situation described above,) would probably carry a heavy fee.
One thing to consider is whether Continual Light and maybe even Wizard Lock upgrade other spells by changing standard spell duration to an open-ended state, similar to Charm Person and Sleep. Thus, Continual Light will persist indefinitely as long as the magical state isn't disturbed. Would bringing other illumination into a magically illuminate zone dispel the illumination?
Knock: A spell which opens secret doors, held portals, doors locked by magic, barred or otherwise secured gates, etc. Range: 6".Knock basically dispels Hold Portal and bypasses Wizard Lock once, but it's notable that the spell doesn't just unlock a door or container, but actually opens them, including lifting timbers on the opposite side of a barred door. A secret door is opened, whether the opening mechanism has been located or not; I would suggest that it will even open a secret door that hasn't been located, as long as the spell is cast on the location believed to contain a secret door.