Most of your attacks create one or more green spaces on the timeline, on and around the icon of the attacking unit. Most enemy attacks create orange spaces on the timeline. When two or more units on the same side have their colored spaces touching each other, they perform a United Attack. Each unit’s attack builds up a combo meter that improves the damage of subsequent attacks.

Attacks with one-handed weapons build up bonus combo in United Attacks, as do any attacks used by Mechs.

If a character who would have participated in a United Attack gets knocked out, you can get a combo bonus for "vengeance." However, knocked-out units don't save their colored spaces, so it's best to put your most injured character at the start or end of the combo.

If you kill an enemy in a United Attack, you get a combo bonus. This can stack.

Attacks that create black spaces can’t link up, and they get in the way of other links. But a particular type of black attack, Conditionals, can turn green or orange—more on that later.

Buff moves are always black. You can’t combo your attack into a 20% defense boost. Parry and Deflect stay black as well.

One technique, Mighty Inch, has a transparent space when selected in the technique list. To color-change it to green, look at the space it goes in, and see if that space would have a color if you hadn't used Mighty Inch. Both green and orange work for this, but it can fail if the source of the color is delayed or removed in some fashion—more on that in Abusing the Timeline.

One unit’s colored spaces can’t stick out past another unit’s icon, even if they’re on the same side, and even if the unit is stunned, bound, or defending. Excess colored spaces will be “blocked” and lose their color.

Enemies build up combo meter significantly faster than you. Don’t let them join up.

If your combo gets up to 150% damage, there’s a chance you’ll get a second United Attack, which the game calls an Overdrive. The chance goes up with the combo, becoming a 100% chance at 200% damage.

In the second United Attack, any colored squares sticking out to the right of the rightmost participating unit icon will be cut off. If there are no colored squares sticking out to the right, the rightmost participant in the first attack will be excluded from the second attack.

There are two confirmed exceptions to that last rule. The first is that if anyone in a United Attack glimmers a new technique during it, the last person gets to participate in the second United Attack. I'll get into the other exception in the Conditionals section.

A lot of boss-only attacks have squares sticking out to the right, so bosses usually participate in a second enemy United Attack.

The later I get into the game, the more often my second United Attack has fewer participants than I thought it should. Maybe there’s some kind of penalty for using attacks with high star costs in the first United Attack? I’m not sure, but they feel unreliable at this point.

In the second United Attack, each character uses a random offensive move on a random target. So long as the move is equipped, they can use it even if they don’t have enough stars, haven’t spent time casting it, or haven’t met the preconditions for it to activate.

I haven’t tested whether a United Attack can bring out a move you haven’t equipped the right weapon for. Probably not.

Courtesy of user Toasty Frosting: in the second United Attack, all techniques are unblockable.

Combo builds slower in the second United Attack. It’s possible to get a high enough combo to trigger a third United Attack, but it’s not very common.

There's a technical difference in how to learn relic techniques in the second United Attack. See my technique guide.

Spells are black while they’re being prepared, but they often get a color on the turn they’re cast.

Conditionals are various techniques that start out black, but move around and sometimes color in when activated.

Take Chain techniques as an example. The first time one of your other units performs an offensive technique that turn, your Chain technique will move one square to the right of that unit’s icon. I'll explain in a moment how the color change works.

Interrupts move you immediately before the enemy who triggers them.

Pursuits move you immediately after the enemy who triggers them.

Counterattacks are weird, and I’ve seen them move either before or after the enemy. I still don’t understand them.

Only one Conditional, either yours or the enemy’s, can trigger off a single technique. I’m not sure how the game determines which conditional to trigger.

If you set two Interrupts of the same type, you can get them each to trigger off a different technique. This is great for interrupting the enemy’s United Attacks.

Some Conditionals can fulfill the conditions to trigger a different Conditional, but I’ve confirmed Chains can’t trigger other Chains.

If a unit icon is in the space a Conditional will move you to, the prior occupant and any icons to the right of it will be shoved to the right. Also, colors extending past the space a unit moved to will be “blocked” as normal. This can break combos.

If there's no room to the right, the prior occupant gets shoved to the left instead. Sadly, you can't shove someone off the timeline.

In your command list, some Conditionals show a black space with a green space underneath it. These techniques always change color when they activate.

Other Conditionals show a black space with a transparent space underneath it. To change color, they need to move into a space that's already colored in, either green or orange.

When turning an orange space green, color is assessed after shoving any units in the way, but before updating the colors to reflect the shove. For instance, if you shove an enemy that has a one-range orange technique, that orange won't move with it, and will color your Conditional green.

Weirdly, moving into a green space seems to be assessed after shoving someone out of the way. If you shove an ally who has a one-range green technique, you won't get a United Attack from it. Investigation is ongoing.

From my testing, "blocked" spaces seem to open up after shoving an ally and before the Conditional actually moves. Let's say the ally with a one-range green technique has another ally two spaces to the left. The ally on the left has a technique that would create green spaces two spaces to the right of it, but the ally on the right is blocking it. When the ally on the right gets shoved, you'll get a United Attack.

Successfully adding a Conditional to a United Attack gives a combo bonus.

Moving an Interrupt to the very end of your United Attack is a gamble. If you accidentally trigger the second United Attack before the Interrupt, the Interrupt won't be added to either United Attack. If you don't trigger the second United Attack, the game will assume the first attack is over, but secretly save your combo percentage just in case. Then when the Interrupt hits, the combo percentage will come right back and potentially trigger the second United Attack.

If you successfully trigger a second United Attack using an Interrupt, the unit that used the Interrupt gets to participate, even if it normally wouldn't.

Showstoppers don't trigger Pursuits. Whoops.

All Conditionals can be canceled by hitting the user with a technique that says “Quell” on it. This also nullifies the Parry and Deflect actions, though thankfully not Defend. Warning: enemies have Quells too.

The Quell needs to actually hit, though. Suppose you use a Quell that does slashing damage. The enemy has an Intercept that goes off immediately before any attack you use that does slashing damage. The enemy hits you before you can Quell them.

When an enemy prepares a Conditional, the name is replaced with question marks. Selecting the enemy on the timeline still shows any relevant damage types, though.

Naturally, Conditionals do nothing if the condition never triggers. This means that if you try to Unleash a Counterattack to get rid of it, and no one attacks you, the Counterattack will still be stuck in your move list next turn.

Counterattacks do nothing if the enemy misses, but activate properly if the user evades. I'm not sure what the difference is between those two things, besides the word onscreen.

Showstoppers activate when a unit that performs a colored attack has no unit icons two spaces to the left of it or two spaces to the right of it.

Showstoppers don’t activate if the unit icon is adjacent or one square away from either end of the timeline.

When a unit meets the conditions for both a United Attack and a Showstopper, only the United Attack activates.

If an enemy dies or an ally gets knocked out before an attack, their unit icon vanishes and isn't considered when determining whether a Showstopper occurs. So don't use that poisoned, heavily injured unit to try to block the boss from getting a Showstopper. (I speak from experience.)

Showstoppers use the stars you didn’t use that turn when assigning actions to your units, so you won’t get a Showstopper if you used every star that turn.

I’m not sure how the game determines stars for enemy Showstoppers.

After the attack you told the unit to use, it will keep using random offensive moves on random targets, only using each move once, until it either spends all the stars or runs out of equipped moves.

Showstoppers have a combo meter, but it only increases damage. You can’t Showstopper twice in a row.

Attacks with two-handed weapons add bonus Showstopper combo, but only when performed by humanoids.

As with United Attacks, you get a stacking combo bonus for every enemy you kill.

As with United Attacks, Showstoppers can use spells and Conditionals. However, spells have their star cost increased by the number of turns they normally take to charge.

Annoyingly, enemies can still block during Showstoppers.

When a unit uses a Showstopper, no other unit on either side of the fight can use a Showstopper for the rest of the turn.

It’s very easy to accidentally hand a boss a Showstopper and have it melt your face off.

If you save your stars because you want as long of a Showstopper as possible, but the enemy knocks out the character who would have used it, you're screwed. Maybe you should have Deflected.

A unit that moves leftward into another unit’s space on the timeline will move the other unit one space to the right, effectively “swapping sides.” A unit that moves rightward into another unit’s space on the timeline will move that unit one space to the left. (This doesn't apply to Conditionals--see above.)

When putting in techniques to make your green spaces join up, the order matters. Suppose Diva, Gourmand, and Boudicca have their unit icons next to each other in their “default” spaces on the timeline. You want to use techniques for Diva and Gourmand that move them each 1 space to the left of their default, you want to use a technique for Boudicca that keeps her in the same space, each technique only makes one green space, and you want them all to United Attack. Put in Gourmand’s technique first, and he’ll move 1 to the left and swap places with Diva. Put in Diva’s technique next, and she’ll move 1 to the left and swap with Gourmand. Now they’re both exactly where they started, and all the spaces link up. Then if you try to get clever and change Gourmand’s technique before finalizing, the game will remember that Diva’s supposed to be off to the left, and you’ll have to undo her technique input and start over.

If timeline position changes, so does the combo. Let’s say you have green space, red space, green space. The technique in the first green space has Delay 1, meaning the target (in the red space) will move one space to the right on the timeline, swapping places with anyone there. The first technique hits, and you have green, green, red, so you now have a combo meter, with the first technique retroactively counted towards the meter, as well as some bonus meter for your ingenuity.

Unfortunately, if you use a Delay to add a unit to the very far right of the combo, not only will the unit you added not be able to participate in the second United Attack, any unit directly to the left of them will be excluded as well. This is one case where Conditionals have the advantage.

Suppose you have red, green, green, green. Again, the technique in the first green space has Delay 1. After it hits, you have green, red, green, green, so you drop the combo and restart it at 100% with the two remaining units. Whoops.

Delay can free up “blocked” spaces. Suppose an enemy’s technique normally colors in one space to the right, but there’s another enemy in that space. You Delay the second enemy by 1. The space will still be colored in, and the enemy will still get a United Attack. (You can check for this in advance by selecting the enemy on the timeline.)

Random Delay techniques used in your second United Attack can break your combo, give the enemy a United Attack, or even give the enemy a Showstopper, and there’s not much you can do about it.

Thankfully, a random Delay that moves an enemy close to you doesn't prematurely end your Showstopper.

If your United Attack kills an enemy that has one or more orange spaces, those spaces will turn green. This doesn’t work for black spaces, and it doesn’t work when smashing inanimate objects.

If a United Attack knocks you out, your spaces just empty out. Small mercies.

Enemies that have already acted have their spaces turn black, so you can’t elongate your United Attack backwards by killing them. Nice try.

Stunned and bound units have their spaces turn black. Stunning an enemy you’re about to kill can cut off a potential combo.

The “Stench” status effect turns all your actions black so you can’t participate in United Attacks. Showstoppers still work, though.

Confusion not only turns the unit's space black, it blackens every space the unit would have turned green.