Building a Construct
The easiest way to make a construct requires a suitable object and an animate objectsspell. If you're not satisfied with a mere animated object, however, you have to put in a bigger effort.
Creating a fairly elaborate construct such as a golem or shield guardian requires the Craft Construct feat (described on page 303 in the Monster Manual). The process of construct creation is just like creating a magic item. The process is described in Chapter 7 of the Dungeon Master's Guide and in Rules of the Game: Making Magic Items. Here are the highlights:
Prerequisites: A construct has a list of prerequisites, which is included in the creation section of the construct's description. A list of prerequisites might include one or more feats, spells, and miscellaneous requirements such as level, alignment, skills, and race or kind.
A construct's creator must have a caster level high enough to cast any prerequisite spell the construct has.
In most cases, the construct's creator must provide any required spells personally; you can't have another character cast them for you, but you can use a scroll that you activate yourself.
Cost: A construct's description (usually) includes a market price and a cost to create the construct. To calculate the creation cost for a construct, subtract the cost of any special materials the construct requires from the market price. Divide the remainder in half. The result you get represents the basic materials you must buy to build the construct. This basic cost includes the cost of the construct's body. Most construct descriptions include a separate cost for the body to allow DMs and players to use the Craft skill to create the body.
The total cost to create the construct is the basic cost plus the cost of special materials. For example, a construct with a market price of 100,000 gp and 10,000 gp worth of required special materials has a creation cost of 55,000 gp. (Here's the math: 100,000 - 10,000 = 90,000; then 90,000/2=45,000; then 45,000 + 10,000 = 55,000 gp.)
Making the construct also requires experience points equal to 1/25th the market price minus the cost of special materials. The construct from the previous example has an XP cost of 3,600.
You can make an advanced version of a construct (one that has more Hit Dice than shown in the creature description). Each extra Hit Die adds 5,000 gp to the construct's market price. If you add enough Hit Dice to increase the construct's size, add an extra 50,000 gp to the construct's market price.
Time: For every 1,000 gp in a construct's market price (or fraction of 1,000 gp), the creator must spend one day working on the construct. The construct from the previous example would require 100 days of work.
Environment: Creating a construct requires peace, quiet, and comfort, just as preparing spells does (even when the creator doesn't need to prepare spells). Any location a character uses for construct creation also must have enough space to hold any special equipment and materials the construct requires.
Equipment: Some constructs also require a specially equipped laboratory similar to an alchemist's lab. The cost for setting up such a laboratory (if it is required at all) is given in the construct's description. The cost for a lab is not included in the construct's market price or base price. Once you set up a lab, you can use it over and over again.
Repairing a Construct
If you have the Craft Construct feat, you can repair damage that a construct has taken. With one day of work and an expenditure of 50 gp per hit point repaired, you can repair up to 20 points of damage to a single construct.
You don't need to make a check to repair a golem, but your DM might want to require one. Use the same Craft skill and DC required to make the construct's body. For example, repairing an iron golem requires a DC 20 Armorsmithing or Weaponsmithing check.
It's also reasonable to assume that construct repair also requires a set of artisan's tools.
A construct that has an Intelligence score acts pretty much like any other creature during an encounter. It reacts and creates strategies to the best of its ability. A mindless construct, however, often proves more difficult to run. Many constructs can offer foes a few surprises as well.
Mindlessness: It's helpful to think of a mindless construct as a fairly simple robot that has just enough built-in programming to allow it to get along in its environment. It can recognize and avoid barriers, obstacles, and hazards. For example, it won't walk into walls or tumble into uncovered pits. It also can operate very simple devices such as levers, pulleys, and doorknobs.
Mindless constructs aren't aggressive (but read on). If attacked, however, they return the favor. The construct strikes at whoever damages it.
A mindless construct has no ability to learn and effectively has no memory, but it can retain and act on simple instructions. A mindless construct's orders must be simple and clear, but they can be general. As a rule of thumb, I recommend keeping instructions to things that can be expressed in 25 words or less, using simple words. Keep in mind that a mindless construct has no capacity to reason and cannot fill in gaps or omissions in its instructions. Also remember that a construct can see and hear, but doesn't have a sense of smell and not much sense of touch (see Part One). In general, a mindless construct responds only to visual or audible triggers.
Spotting a Construct: Most constructs resemble inanimate objects when they aren't moving themselves. A simple animated object is indistinguishable from a regular object until it moves (though a detect magic spell will reveal the magic aura from the spell that animates the object). When an animated object moves or acts, it's fairly obvious the object isn't quite normal. A character can make a DC 26 Spellcraft check to note the spell in play.
Permanent constructs, such as golems, usually offer a few clues that can alert an observant adventurer to its true nature, even when at rest. Such clues can include articulated joints, gemlike eyes, and weaponry and bits of equipment that aren't part of the creature's main structure. A DC 20 Spellcraft or Knowledge (arcana) check ought to be sufficient to reveal these clues.
That concludes our look at constructs. Next week we'll consider the living construct subtype.
About the Author
Skip Williams keeps busy with freelance projects for several different game companies and was the Sage of Dragon Magazine for many years. Skip is a co-designer of the D&D 3rd Edition game and the chief architect of the Monster Manual. When not devising swift and cruel deaths for player characters, Skip putters in his kitchen or garden (rabbits and deer are not Skip's friends) or works on repairing and improving the century-old farmhouse that he shares with his wife, Penny, and a growing menagerie of pets.
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