Thanks for clarifying this. It’s good to know what is intended.
Just for reference, I would not read “If a Troop is already in last position when the Terror triggers, they will run away from the battle” to mean a troop in slot 1, 2 or 3 could flee. I’d see that as them having to move down slots until they reach last “position”, meaning slot 4. Because in-game effects that move an enemy to “last position” ALWAYS move them to slot 4. I feel like the confusion regarding the terms position and slot being used to mean different things is similar to how “turn” and “move” sometimes get used to mean different things and that’s been pointed out on here before. If you’re trying to be clear, it would be a big help to clarify when giving new information what terms mean if there’s two similar terms being used, like this (I seem to remember when Journey events were launched your team did a good job of explaining the scoring regarding turns and moves, as an example). I know it’s easy to overlook stuff and that’s why it’s great to get clarification like these, but not everyone sees replies to posts on the forum, so it’s better to settle stuff up front. Thanks.
I also encountered that phantom troop in epic trial. It happened in 2nd slot. When the top troop of the overlapping two died, the bottom one showed up, and took several skull hits in following turns, with damage shown, but without effect on its armor and hp. The other remaining troop was barriered knight in 4th slot, and its barrier remained on, as skull damages hit the phantom in 2nd slot. I couldn’t inflict enough damage to phantom before my own team wiped, so I can’t tell whether that seemly invulnerability is just a display bug or the phantom truly untouchable.
(emphasis mine)
Good to know! Personally I might explain it as:
“Troops affected by Terror have a 10% chance to either hide behind (swap places with) the next ally below them, or if they are the last Troop in their team, run away form battle … cowards! (Terror is resolved from bottom to top when multiple troops are affected.)”
I don’t think we really have a clear distinction for the 2 terms internally either and they’re often used interchangeably.
I think sometimes we don’t realise how our words will be analysed when we use them in the community - so while some things are established and have official definitions, other words are just a general label which we use with the assumption the context of the whole post/discussion will clarify and make unambiguous. Also some words we pick up from the community and aren’t even words we have previously used internally. I try to keep up with the lingo 
When I make sure this is written properly in the Help Center do you think it would be most clear if I explain it like:
“If no Troops in the Team are below the Troop afflicted with Terror, and Terror triggers, the Troop will flee the battle”
^ I will be double checking if we usually use the words “afflicted” and also I need to double check “flee” vs ie “run away” etc. as I do try to use all the official in game terminology in the Help Center.
… Slightly off topic side note: My favourite are unofficial names for Troops.
Although they make it hard to remember the official Troop names sometimes.
I cannot tell you how long it took me to remember Prince Ethoras’ and Penglong’s names.
Ethoras is an anagram for what we were calling him internally before he had a real name.
Penglong will forever be known in my heart as Longboi <3
Just to add to this, I like renaming the pets.
The new PvP bat pet. Iv called Christopher lee.
And the dog PvP pet, iv called sausages
Can’t speak for everyone, but that seems really good to me. Very clear and easy to understand, which makes a bug difference. Thank you.
Seems kinda wordy…
*The last Troop in the team will flee the battle if Terror triggers. * followed by something to the effect of each troop being polled bottom to top allowing all troops to potentially flee if all are afflicted.
It’s hard to put in words.
But if your using
Orbweaver and Meg
Kill the bottom 2 and the troop in 2nd has terror, it’ll flee.
Not just move down one.
That’s the best way to explain it I think. 
For those, who’ve fallen from the moon. During this Bounty event my Sister of Nightmares has inflicted this effect on 2 (third and fourth) enemies. Couple of moves after they fled concurrently.
Can’t imagine this situation to be both “correct” and “as intended”
Apparently it is.
In theory, there’s like a one-in-a-million chance of a whole team inflicted with terror all fleeing at the same time, and from what’s been said that’s supposed to be an option. Just hope that if it ever happens, it’s the enemy team.
One in 10,000, technically (10% ^4), but yes.
Compare the hero talent “Rising Shadows” – 7% chance to kill the last enemy upon any enemy dying. Yes, this means that each activation is also a 7% chance to re-trigger itself, and yes, there is actually recorded video of the trait triggering 3 times in a row (aka. instant TPK) …