Basic Units[]
The Prince[]
The Prince is the main character of the game, as well as your starting unit. He is a melee class that can only block one enemy, and may seem lackluster compared with the blocking abilities of the Soldier and Heavy Armor, the point gain of Valkyries or the dodge chance of Rogues. However, he is not to be underestimated- chances are he is your highest-level unit, his attack power is decent, and he brings two powerful passive abilities to the field. When deployed, all your other units gain a percentage of Attack and Defense depending on the level of the Prince, plus the bonus from your Title. Place him early in a non-critical position somewhere in your back field and reap the benefits for the entire match.
Soldier[]
The Soldier is your basic melee workhorse- can initially block two enemies and 3 after CC, with higher Attack but lower Defense than Heavy Armors. Early in a match they provide your primary source of blocking, but later on they can provide pinch blocking when a Heavy Armor goes down or be used in conjunction with Archers to thin out enemy ranks. Every team can benefit from at least 3-4 Soldiers. Notably they are also generally the units which have the Call Reinforcements skill, substantially increasing the speed you can get high cost units onto the field.
Archer[]
The Archer is your basic ranged unit, and are essential to most teams. Being your low-cost ranged attack option, they provide necessary damage against flying enemies, especially in missions where the enemy rushes flyers against you early in the match. Despite being low cost, Archers are not to be underestimated. A decent Archer can put damage on enemy heavies, thin out mobs of lesser enemies, and team up nicely with Soldiers and Heavy Armors to add damage to blocking enemies.
Heavy Armor[]
The Heavy Armor looks intimidating, can block three enemies, and has great defense and HP. However, they need support from other units- a Heavy Armor on it's own can't accomplish much except buy you time. Your standard wall configuration is a Heavy Armor and a dedicated Healer, which makes an excellent backstop to catch any units that make it through the rest of your units. They are also excellent when combined with Mages, bunching units together so the Mage's AOE attacks can take them out. Another effective combination, particularly on maps where several weaker enemies spawn right before a heavy, is to place a Heavy Armor one space ahead of a higher-attack unit such as a Rogue, Princess or Valkyrie. The Heavy Armor will absorb the attention of the weaker foes while the heavy moves on to your higher-attack unit.
Healer[]
Strategic use of Healers is essential to playing Aigis, especially if you are trying to earn three stars on every map. Healers automatically target the unit with the lowest HP in their AOE, and any bonus to their "Attack" increases their ability to heal. Because a Healer can only target one unit at a time, it is possible to "overwork" a Healer by placing too many other units in their AOE. A Healer will not be able to provide effective protection to more than 2-3 units, especially if the Healer is taking damage itself. Depending on the situation, two Healers with overlapping AOEs might be less effective than having them more spaced unit- Healers can very easily end up targeting the same unit at the same time and wasting the second heal when that unit hits max HP. Finally, don't underestimate the power of the a dedicated Healer supporting another class. A Healer + Witch, Healer + Valkyrie or Healer + Bandit on the front lines of any map can prove effective at thinning out enemy forces, and once placed you can usually ignore them and focus on critical chokepoints.
Mage[]
Mages are probably the single most important unit in the game. They provide ranged magic damage in the form of an AOE fireball, that ignores enemy defense. Mages seem to universally have high Unit Cost, however, meaning you can't usually take more than 1 or 2 on any team unless you're building with a specific strategy in mind. Learning to place your Mages is crucial- the combination of a Mage with a Soldier or Heavy Armor is obvious, but also consider having a Witch lead a Mage- the Witch's slow effect will usually group units together to be cut down by the Mage's fireball.
Situational Units[]
Rogue[]
The in-game tutorials don't cover Rogues, which is really too bad as, once mastered, the Rogue class is one of the most effective units. They all have a fairly high dodge chance, high attack, and most importantly many of them have the "Assassinate" power. They excel at killing enemy mobs, and can be used to block stronger enemies. Because of their high dodge chance, they can be used in conjunction with a Healer to "dodge-tank" powerful enemies. Getting Rogues with Assassinate out in the early-to-mid-game is crucial- you're going to want to have that Assassination power charged up for tough enemies in the late game. There is nothing quite like seeing a lucky Rogue with Assassinate insta-killing a mob of enemy heavies to close out a match.
Bandit[]
Bandits are the big meat of the group. Their Defense is pitifully low, but they boast sky-high Health and Attack values, even outstripping other units of higher level and rarity. While lacking in utility like most other units, Bandits can soak incredible punishment and dish out a beating themselves, making them quite useful for smashing apart small mobs or stalling a single big creature. For cases where unmitigated violence is required - a point only exaggerated by the fact most Bandits have skills that further boost Attack - you need to look no further.
Valkyrie[]
Valkyries have a very useful ability- you earn an extra Unit Point every time they kill an enemy. They are very balanced stat-wise, but since many key melee units have low attack to begin with they will probably have better Attack than a good portion of your melee force. They are most effective in the early-to-mid game, where they can cut down hordes of weak mobs and give you access to your high-cost units that are crucial in late game like Mages and Healers. They're also one of the only melee units to have natural Magic Resistance, a great boon when an enemy Mage or Witch comes down the line. Unlike other units, retreating them gives you back 70% of their cost, and this rises to 80% after a class change.
Princess[]
Princesses might be considered a magical variety of Valkyrie, possessing a high Attack stat, decent Health, and some Magic Resistance to boot. They are more expensive, and can't generate Unit Points like a Valkyrie, but they are stat-wise more powerful and deal magic damage on attack, meaning they can and will rip armored enemies to shreds with a bit of healing support. Once mid-to-late game kicks in, swapping in a Princess can grant a much-needed offensive edge to your fighting force (or, in the case of Lilia plus her skill, a rather hard-hitting tank).
Witch[]
Witches inflict ranged magic damage and temporarily de-buff an enemy's speed. What effect this has depends on how your current map is spawning enemy mobs- Witches tend to cluster-up enemies that are spread out, making them easy prey for Mages, or thin out enemies that are already in big clusters, which relieves pressure on your Rogues, Valkyries and Bandits. On maps with lots of enemy flyers, they provide excellent support for archers, slowing down the enemies so archers have more time to take them down. Because of their Magic damage they ignore enemy armor, which makes them good against heavier units, which they can further slow too, nearly stopping them in their tracks. Combined with a Mage, they are the bane of heavy units.
Samurai[]
Samurai are a melee class that attack all enemies they are blocking. They are perfect for wiping out monsters that push forward in swarms.
Ninja[]
Ninja are characterized by the ability to perform ranged attacks while being a melee unit. With their high attack speeds and attack range, this class has tactical uses that other melee units cannot match.
Unique Units[]
Dragon Princess Anya[]
Simply put, a more defensive type of Princess that can block 2 units instead of one, a hybrid of a soldier and a princess. While significantly weaker in attack than other Princesses, her HP and Defense is higher to make up for it, and she has a special skill to half physical attacks against her. This, combined with her defense ignoring attack, makes her great for groups of heavy armor. Unfortunately, unlike other princesses, she lacks magic resistance and has a very high cost of 35, so take that into consideration when deciding to use her.
Dragon Shaman Echidna[]
A healer that becomes a mage when her skill is activated. Because of this, she is more expensive than a CC'd healer though still less expensive than a CC'd mage. She is extremely useful as she is comparable in power to a CC'd Mage or Healer without needing to be CC'd, and much of the time, mages are more situational than healers. That said, she is still a jack of both trades, and her ability takes a good amount of time to recharge. She is best paired with a heavy armor or a witch as both healers and mages have a strong synergy with the healer and mage classes.