Okay so, I've been combing the core book looking for the mechanic having to deal with held actions, because it mentions being able to do it several times, but I don't think it actually has a section that explains what you can do with held actions, or even how they work with the initiative.
I know that blocking, dodging, and cover make a small mention that you can spend an action for the initiative to use them, but that's now helpful. If, per say, a sniper character was to hold their action to wait for their target to come out of cover, could they spend the action whenever they wanted to fire where they were aiming? Would a held action carry over into the next initiative?
I know there's an aerial maneuver that specifically requires three actions. Not two rounds, for four actions, but three consecutive actions. What I find really confusing about this is how would one go about resolving this? Would the maneuver be resolved on the first round, with the first action when it's used, or the last action in the second round, when all the actions for the maneuver are spent?
Some held action stuff is...vague. Like technically it says you can hold actions and use them, but when can you use them? Do you have to set conditions, can you interrupt other people in the middle of their actions, if you don't use em during the round can you wait until the end to do so? It's all...vague.
My group which has been playing FoE for about...god 3-4 years now have used held actions like this: You can hold an action(s) as you wish. You cannot interrupt someone doing something (say an enemy announces they are attacking your ally, you cannot say I used my held action to attack him first) but you can use your action before someone else declares what they are doing (say an enemy gets an action, he is deciding what to do, during this time you say decide to take a dose of med x, that's fine). When the round ends the GM then declares round over and asks if anyone wants to use held actions, if yes, they do so. This may not work for you but take it as you will, it has worked for use well so far.
As for needing three actions, that one is incredibly tricky. I believe the one you are referring to is Sonic Rainboom? If so it outlines explicitly what each action does. You have to use them each chance possible. Here is a good outline
Round 1 Action 1: Move in straight path at normal flight speed
Action 2: Move in straight path at double flight speed
Round 2 Action 3: Move in straight path at double flight speed. At end of move speed Rainboom occurs.
Action 4: Do whatever
Apologies for any confusion on this, I can make an update to make held actions a little less vague, as soon as I nail down exactly what it is that would help most with clarity. Short Answer: ONeal is pretty much correct.
Let's start with the basic scenario: Initiative order in Combat with a group of three enemies. Let's say they're raiders with rifles.
You have three players, A, B and C, and your GM, who has opted for all three raiders to act as a single group.
Your initiative is:
GM (3 Raiders)
Players get 2 actions added to their "queue" when their initiative occurs. They may choose to hold as many actions as they like, but only one held action is "saved" between combat rounds.
Actions which are held can be used to either dodge/block/take cover, assist an ally, react to an attack which has occurred (a slightly nebulous area) or as part of that player's next turn.
Player A has a Pegasus character that chooses to spend one action moving and shooting (Perk: Run n' Gun) and would like to hold his second action. He takes his shot, and has one action held.
Player B is terrified of getting hit, and holds both actions to have dodges against the raiders, who are known to target unicorns for their delicious horns.
The GM takes their turn for the raider group. The raiders spend their actions taking pot-shots at the unicorn, as predicted. They roll to target, and three shots hit. One shot each hits characters A, B, and C.
A takes the hit to their armor. The armor soaks enough damage to prevent a wound, but degrades a little.
B uses a Teleport dodge. The teleport is successful, and they blink away before the shot connects. They still have one held action.
C uses a "potential action" - an action they would be granted this round - to jump behind an adjacent wall, which takes the brunt of the bullet and stops it from dealing as much damage. They still take a wound to the torso.
Before the turn ends, B uses their held action to move over to C and cast a Heal spell on them. (Perk: Dash Casting)
Now it is C's Turn. They have one action, which they choose to hold between rounds.
Combat round 2:
A (1 Action, 2 Potential)
B (0 Actions, 2 Potential)
GM (0 Actions, 2 Potential)
C (1 Action, 2 Potential)
A now takes their turn. They have three actions as of their initiative phase, so they COULD pull off a sonic rainboom in the center of the enemy combatants, ruining their day. They would also collide with the ground, because they don't have the altitude they need. Instead, they choose to pull off a buccaneer blaze (Because they're so awesome they know two separate rk 4 maneuvers). They spend two actions moving through the enemies and lighting the area on fire.
B has played it cautious for too long. Now that they have some cover, they state that their horn begins to glow visibly with a prepared dodge action, and hold both actions in preparation for what's to come.
GM turn occurs, and scorched raiders now completely open fire. They focus on the Unicorn, now that the pegasus has effectively spent all of their altitude. Firing only at the visibly-glowing unicorn, they land 5 hits out of 6.
B uses both held "dodge" actions to pump a single layer of overglow into a casting of Return to Sender.
All five of the bullets are grabbed mid-air and sent back from whence they came, killing all three of the raiders.
Even though combat is over, C still has three actions to spend. They do a sonic rainboom, just because they can.
I hope that clears things up a little bit.
TL; DR - you can't interrupt others' actions, but you CAN respond to them after the action is taken. Only dodge actions can be taken immediately as a response. Otherwise, response actions are taken between that turn and the next turn in the initiative.
A player has a zebra, who, for some reason, sees fit to use the Change Your Stripes ritual in Combat.
Action 1: Chanting, mumbling. Target may feel some sort of prickling as the magic begins to condense around them.
Action 2: Chanting, rhyming at a consistent cadence. Target begins to have visible effects on their person.
Action 3: Louder chanting, speaking in zebra tongues and rhyming babble. Though you listen, you cannot understand the words being said. The magical effects are visible as the color change progresses along the target, who probably is starting to be rather upset by now.
Action 4: Chanting and babble reaches a crescendo. The target's exterior glows visibly as they are completely enveloped by the magic. They probably have a serious freak out right about now.
Action 1: Ritual Completed! The target is now an embarrassing combination of cyan, lime green and hot pink.
Action 2: 3 second victory dance.
I....thank you so much right now because this answers quite a bit. My group never at all realized we could save an action between combat rounds. It suddenly makes certain things (like rainbooms) possible. This is amazing. Thank you for this clarification once again Archer.
To be honest one person in my playgroup played a medic/e-weapons expert that amazingly never took the run and gun (or any of the others) until roughly level 15 or so. Was...he has since never not gone without one of them ever again.