They join late in the game, but they're pretty useful. Kind of a jack-of-all trades, they're decent at everything but good at nothing. Most of their field skills radiate out from them in 3-square radiuses, which is a pretty large area. Their elemental attacks aren't great, but their healing and instant-death attacks are very useful.
Although they're powerful, they're not all they're cracked up to be. Their physical strength is high, and their swordtechs can be fairly useful both in melee and field versions, but their low max SP means they can only do a few of them per battle. Still, they're always good to have around. 8-)
Dragnar is identical to Summoner in every way, shape, and form; her stats are a little higher, that's all.
Big and strong, although magic tends to hurt them badly. Having one of these in the party in a melee battle means you have a chance that you'll defend against half the damage of any attack automatically (even without choosing "Defense"). Their Smashes are some of the most powerful single attacks in the game. However, their low SP means they can't do too many of those in one battle. Since they have no field attacks, pair them with Light Armors so they can move quickly.
Very similar to Heavy Armors, they're just a bit faster and weaker and better against magic attacks. Having one in a melee battle means all characters have a chance of their physical attacks doing double damage. Another good candidate for a Light Armor to accompany.
Their field attacks aren't that great, although having a unit of four Lancers can do some good damage. I recommend against using them like that, though, because they're far more useful split up. They can give you more or less free EXP! Their Javelin attacks only use 1 SP per use (most of them) and can be used on the field, netting you EXP every time. Put them with any party that tends to lag behind (e.g. any party without Light Armors) and if you happen to not be able to move, just Javelin for free EXP. Very nice! In melee battle, their attacks hit all enemies at once, again for little SP, although they're weaker than most.
One of the most useful classes in the game. Having one in your party means you can move up to 10 extra squares per move - this makes a HUGE difference! As well, their attacks in melee battles, although fairly weak, hit all enemies at once. They use up gobs of SP, though, so you can't use it too often. Put these with Knights or Heavy Armors or anyone else who doesn't have a good field attack.
These little guys are very weird. In melee battles, they can't be controlled at all; they'll do a Dance automatically. In the field you can tell them to Dance as well, but any Dance will always be completely random. There are three different types of dances depending on whether you're paired with a "special" dragon; see Tips for a discussion on them. They're easy to upkeep, at least: no equipment and their Dances take up no MP.
Extremely useful at the start of the game, they start getting a bit overshadowed by dragons' Refresh spells later on. But anyone who can heal is useful! I recommend putting three of them with a Lancer and switching the fourth one out depending on whose level gets higher. Don't underestimate the Exorcism spell, either: it can work wonders! Their attack spells, as you might expect, aren't great though.
Although Matelite's probably the strongest physical attacker in the game, he doesn't have any variety at all. His Inspire can be used on the field to destroy auto-cannons, bridges, and the like, but it has almost no range and isn't that powerful. However, it only costs 4 SP, so it can be used quite often, especially in later battles. If he's paired with a Light Armor and fights a lot, he can still be quite useful.
An extremely useful character. The Summons do THE most damage of any field attack in the game, consistently. They can also use three useful spells (healing, fire attack, and upping attack power) in case there's no enemies around. Pair them together with either a Wizard or Priest (depending on whether you want to use them for healing or attacking when they're not summoning) and a Light Armor.
Unless you've got at least three of these together, their field attacks won't do much damage. In battle they aren't much better, either. Their main use, IMO, is to manipulate the field by burning forests, destroying auto-cannons or structures, or icing rivers. I recommend having three of them with a Lancer and switching out the fourth depending on whose level is highest.
Specials and Stats
Here's a table of which special levels up with which dragon statistic. E.g. if the party has one Knight and the associated dragon's Strength stat is at level 4, they'll have Critical at level 4. If they have two Knights, it'll be at level 8. If they have three it'll be at level 10, because it can't go higher than that.
The Specials not mentioned here all go up with individual elemental stats (see Techniques and Spells).