After the offensives, parry-based defensives are the easiest style to master, though there are also dodge-based defensive warriors out there (the dodge-based defensives are harder to win with in basic).
1) Design
In creating a pure defensive, the things that you should be concerned about are: Hit Points, Carry Ability, Endurance, and your skills in parry and/or defense. Again, other attributes and skills can't hurt, but those are the vital attributes for how you'll be fighting.
Hit Points come from Constitution (mostly), Size, and Will. Carry Ability comes from Strength and Constitution, though if your Strength is lower than your Constitution, the carry ability only comes from your Strength.
Endurance comes from Strength, Constitution, and Will (especially Will). You get Parry Skills at Str: 5, 7, 15, 17, 21, 21 Siz: (5), (7), (15), (17), (21), (21) Wil: 5, 7, 15, 17, 21, 21 Dft: 5, 7, 9, 11, 11, 13, 15, 17, 21, 21 You get Defense Skills at Siz: (5), (7), (15), (17), (21), (21) Wit: 5, 7, 9, 11, 11, 13, 15, 17, 21, 21 Wil: 5, 7, 15, 17, 21, 21 Spd: 5, 7, 15, 17, 21, 21 Dft: 5, 7, 9, 11, 11, 13, 15, 17, 21, 21 Note that for parry and defense skills in size, you get penalized for having higher sizes.For parry based styles, it is highly recommended to have 11+ strength and as much will as you can get. Eleven deftness is also very nice. You can't have too much constitution. It is recommended to not be too big, because you don't typically have enough points for the stats you really want. Wit is nice, but not necessary. Almost always, 1 point of con is better than 1 parry skill.
For dodge based styles, it is much tougher. ABs are usually made with 21 deftness because they get attack skill bonuses, but for a pure defensive dodging AB, the deftness isn't as vital. If you're going open handed, strength can be sacrificed. I do not know as much about pure defensive ABs, especially in basic. For Lungers, you want lots and lots of endurance. Twenty-one will and as much strength and constitution as you can get. Low size is highly recommended for dodge based defensives. Somehow you also need to have enough defense skills from your other stats to be able to dodge. High speed is not desired on either, simply because you want those points elsewhere. Simply because of all the parry & defense skills, 11 deftness is suggested as a minimum.
2) Style Choice
For parry based defensives, any style that learns parry naturally works fine. Style is almost irrelevant, because in most of these fights, a couple of parry skills or endurance burn doesn't come in to play. There are times when it does, which is what makes Total Parries the king (good endurance conservation and best natural parry in the game), but all of these styles can be very, very successful as pure defensives.
Total Parries are the most common pure defensive on the sands. There are plenty of nicknames for Total Parries who are pure defensives, because of how frustrating it can be to face them. They learn parry and defense skills naturally, are well suited to all of the shields, and often ignore opportunities to attack. They also have the highest parry base in the game.
Parry Strikers would be my next choice. They conserve endurance better than any of the other parry based pure defensives. They learn parry naturally. They are well suited to the Small Shield.
Parry Ripostes conserve somewhere around the same level as Total Parries. They learn parry skills naturally. Because they also learn so many riposte skills, even running defensive strategies they will tend to try to gain the initiative. They are one of the best natural hybrids, but they make fine pure defensives as well.
Parry Lungers burn endurance much faster than the styles listed above. They have much higher skill bases overall, but their parry is the same as Parry Ripostes and Parry Strikers. They learn parry naturally.
Wall of Steels have the potential for the highest parry in the game. Total Parries will never be bonused in parry skills, so while they start with the most, a Wall of Steel can be bonused and start with two more parry skills than any other style can. On the other side of things, they burn endurance faster than any of the other styles listed and typically use heavier weapons. Like Parry Lungers, they have a higher overall skill base, but for the discussion of the pure defensive, those other skills don't matter as much.
The other option is a dodge-based Pure Defensive. Most of the time, these styles are run as hybrids in later minutes, but they both have the ability to run as pure defensives for an entire fight.
Lungers are the king in basic. They learn defense naturally and have the highest starting defense in the game. In fact, they are the only style other than Total Parries that learns defense naturally. On the down side, they burn endurance fast.
Aimed Blows are the other style that typically runs as a pure dodge defensive. I do not know much about these warriors, but watching them is a thing of beauty. In ADM, when they can start going open handed without concern, they rule the game, but even in basic, they can be very successful. The down side for them is that they do not learn defense skills naturally, so you're really hoping it is their favorite learn.
As always, any style can be run as a pure defensive, for part of a fight or an entire fight. The styles listed above are merely the traditional choices. And realize that the dodge based styles I list are often run as hybrids in later minutes. The line between a pure defensive and a hybrid is often blurred, because even some Total Parry pure scum will attack and win fights after their opponent is exhausted (which is one of the hybrid strategies I will mention later).
3) Weapon Selection (with requirements)
If you aren't planning to attack, it hardly matters what weapon you use, right? Typically, parry based pure defensives use an off hand shield (and often a main hand shield) Large Shield (13 Str, 3 Wit, 7 Dft) (10+ Dft to use in off hand, depending on Main hand weapon) Medium Shield (9 Str, 3 Wit, 5 Dft) (7+ Dft to use in off hand) Small Shield (5 Str, 3 Wit, 5 Dft) (7+ Dft to use in off hand) ABs often use their Fists, because they get a bonus to their ability to dodge. As with style choice, weapons selection often does not matter for these fights. The fight outcome is more a function of your opponent's ability to take you down or wait you out, not on your abilities or skills. Main hand weapon is whatever you are well suited to. BA (requies 15 str, 7 wit, and 11 deft; plus 9 size if using an off hand) is a nice high damage/low wit choice. SS is a nice low wit choice for some other styles (9 str, 5 wit, and 7 deft). For a dodging warrior, LS might also be a good choice (11 str, 9 siz, 5 wit, and 9 deft).
4) Strategy and Tactics
For your parry based pure defensive, 1-1 Parry or 1-1 Open works great. The response tactic has some interesting uses, especially in minute 1 or minute 6. Note that this strategy will usually make your fights quite boring to read, especially the 1-1 parry strategy. This strategy and type of warrior is not meant to be fun, but good ones can amass amazing records, especially before Advanced Duel2. Your best challenges are styles that burn their endurance fastest (Lungers, Wall of Steels, and Parry Lungers) or any warrior that does average damage and runs hot (Many bashers, slashers and strikers). Stay away from Aimed Blows!!! Really not recommended for a parry based defensive to run higher than 6-6 in minute 1.
For the dodge based pure defensive, High Activity Level is important. How high depends largely on your warrior. Experiment to find what works best. Offensive Effort is typically low. Dodge or Open for tactics.
Once again, the line between pure defensive and hybrid can become very blurred. Not attacking at all may not be your best way to win fights. What if in a later minute you raise your offensive effort and do not use a defensive tactic? You're suddenly not fighting as a pure defensive. For many warriors, this is a much better strategy than simply trying to wait until your opponent drops from exhaustion. The mechanics of the game can allow for some very strange results. I had a basher with very little endurance and 3 will refuse to drop from exhaustion and finally won after 6 minutes against a total parry. This is probably more important for dodge based defensives, but can also be true for parry based defensives.
5) Armor
APA/F is the norm. ASM/x is a nice choice, especially against that nasty SC. For dodging defensives, I've experimented a lot and don't have a conclusion as to what armor is best. I try not to overencumber for a dodge warrior, but even though warriors don't dodge as well with APA/F, it is not clear to me that you shouldn't wear APA/F.