Here is a page regarding status effects. The Last Story offers many different statuses that can be inflicted by enemies, inflicted weapons, or entering a magic circle. You can cure all of the bad statuses by entering a heal circle. The status effects can be good or bad; some are special to only the user.
Downed is an effect that causes the character to stay down after they have lost a life. To cure it, Zael has to have Gathering activated as well as run over the selected character to cure him/her. Mirania's Revive can also resurrect downed characters as well as knocked out characters.
KO is when a party member has lost all of their lives in battle, and therefore cannot be revived over time or by Zael's Cure. But if Zael is KO'd, you get a Game Over. Only Mirania's Revive can bring a KO'd ally back into battle.
Poison is an effect that causes the recipient to gradually lose health over time. Poison can't kill you, but it can decrease your health all the way to 1 if you don't cure it quickly enough. You can cure it by entering a heal circle or letting it disperse by itself. Vipers are the most common enemies found to give venom just by attacking them.
Sticky is an effect that causes the recipient to move slow. It eventually wears off over time or you can roll around to let it drip off faster. Sticky causes the recipient too slow that even jumping over things or trying to Vertical Slice may be impossible. Sea Reptids and Stinky Ogres are the most common enemies found to spit out sticky fluids. Mad Kraken can also inflict sticky. The weapon Leek has a 10% chance to inflict Sticky on your opponent.
Usually when an ally has been inflicted with Sticky, you'll hear them complain about it.
Silence is an effect that causes the recipient unable to use magic (or the A skill, such as Gale). Over time it will disperse, but it's for the player to decide if he/she will want to use magic. Enemy sorcerers are the most common enemies found to inflict silence; but your party members must enter the Silence circle to be inflicted. To cure silence made by sorcerers, you can step into a heal circle, let it disperse by itself, or defeat the inflicter. The weapons Chair and Hammer have a 10% chance to inflict Silence on your opponent.
Instant Death is considered as an effect that causes the recipient to instantly die, or lose a life in this case. There are no known enemies that cause this effect, but only your characters can cause it to your opponents. The weapons Hoe and Axe both have a 1% chance to inflict Instant Death.
Paralysis is an effect that causes the recipient unable to move for a short time. It can disperse by itself or the player must move their joystick back and forth. You can also use Calista's Deflector ability. You can also cure it by entering a heal circle, but you must be in that circle before the paralysis happens. Muruk and archers are common enemies found to shoot the party with paralysis needles/arrows. The weapon Pitchfork has a 5% chance to inflict Paralyze on your opponent. Syrenne's Spirit Attack, Shadow Stitch can also inflict Paralysis.
Daze is an effect that causes the recipient to be dazed for a short time. It can disperse by itself or by waving your joystick back and forth. It can also be cured by a healing circle or by Ancient Barrier, you must be in those before it happens. Daze can be inflicted by Daze Bombs which are green cylindrical bombs used against bosses like Marbas and Cocoon online.
Doom is an effect that causes the recipient to have a 30 second countdown for them to react. When the the countdown ends, the recipient dies or loses a life. To cure the status, you must enter a heal circle or you can deflect them back. The final boss and Kraken are known bosses found to give you Doom. Dagran's Spirit Attack, Death Sentence inflicts Doom on every opponent in the battlefield.
Shade is an effect that causes your party members (excluding Zael) to react on their own and attack each other. To cure it, the player must run into a heal circle and diffuse it to spread the heal to your party members. The bosses Lesser Shade, Shade, and Dark Muruk are known to give Shade. You can deflect Dark Muruk's needles with Deflector.
Petrify is an effect that causes the recipient to turn into stone. The weapon Lance has a 10% chance that inflicts petrify. Stone Blades (Reptid) are known enemies that are able to petrify you when hit with its sword. To cure it, the players must wave their joystick left to right until they break off.
Nitro is an effect that causes the enemy to gain speed and strength. On the way to the Outsider, the Reptids released from the dungeon seemed to absorb its energy, causing them to have the effect. However, it isn't explained how some of the enemies in the Arganan Temple possess this effect.
Stop is an effect that causes the enemy to be stopped. When Gathering is at max, Zael must deactivate Gathering to Burst, and that will cause surrounding enemies to be stopped. They cannot move, so Zael and his party members have an opening to the enemies. Some stronger enemies such as Cave Cougars are resistant to being stopped and can only be slowed at max burst.
Guard Break is an effect that causes the recipient unable to guard and decreases their defense. For the party members to inflict it, Yurick must cast Prominence and Zael must diffuse the magic to let it spread to nearby enemies.
Break is an effect that causes the recipient to lower their defenses. For the party members to inflict it, Yurick must cast Flare, which is the predecessor of Prominence and Zael must diffuse it to spread to nearby enemies. Braziers are knockable objects used to act like a Flare circle as well. In Co-op Multiplayer, some bosses can also inflict Break. By curing it, the player must enter a heal circle, and it's up to that player to diffuse it.
Slip Fall is an effect that causes the recipient to repeatedly slip when they move. To inflict it, Lowell must cast his ice magic and you must diffuse it to inflict surrounding enemies. Muruk online can inflict it. To cure it, stand still, enter a heal circle, or diffuse Muruk's ice circle.
Deflector is a helpful status that causes the recipient to be protected and deflect any projectors. To inflict it, Calista must use Shining, and the player must diffuse the holy circle. It will wear off on it's own, or if Calista is defeated.
Accelerate is an effect (and Spirit Attack) that causes Zael and the party members to increase movement speed, casting speed, and attack speed. To spread it out to the other party members, Zael must use Gale. It will wear off eventually. There is also an item online that lets any member accelerate, but only that character and you cannot spread it onto another member.
Ancient Barrier is an effect (and Spirit Attack) that causes Zael and party members to be invincible for a short time. To spread it, Zael must use Gale. It will wear off eventually even if Calista is defeated. There is also a rare item that spawns online that gives you this effect. You cannot spread it.
Regen is an effect that causes the recipient to gradually heal their health over time. To gain it, the recipient must enter a heal circle. To spread the heal or cancel the heal, the player must diffuse the heal circles. Enemy healers, heal bombs, Calista and Mirania can cast Recover. Their circle inflicts regen. This also blocks the effect of enemy damage circles.
Berserker is a passive effect that when activated causes Lowell to gain a large boost in strength while sacrificing defense. this status will stay active until Lowell switches back to magical attacks , its can only be used when performing the Berserker Skill.
Strength Up is a passive effect that causes Zael or Dagran to gain strength for a temporary amount of time. It wears off eventually, and can only be used if you perform the Power Strike skill.
Counter Up is a passive effect that causes Dagran or Syrenne to gain defense for a temporary amount of time. It wears off eventually, and can only be used if you perform the Full Guard skill. It can also be used to act like Gale, to "diffuse" magic circles. It can also act like Gathering but by catching enemies attention only.
Chain Up is a passive skill that causes Syrenne to easily make chains for a temporary amount of time. It wears off eventually, and can only be used if Syrenne uses Power Chain.