These are the two questions from the start of this thread that can give some insight into your question. Can't change the numbers here, but they are actually #12 & 13 from the Attack section.
Q: Can a Knight attack a creature through his Echo if only the Echo has line-of-sight to that creature? Is there any penalty if the Knight can’t see the target? A: No by RAW, because the Echo has no "senses" without you using the level 7 ability. Thus an Echo cannot help a Knight see her target. (thanks @LeviRocks)
Q: If a creature has obscurement or cover from the Knight, but the Echo has a clear line-of-sight, is there any penalty to the attack if it originates from the Echo? A: No, because the attack would originate from a position that wouldn't have the cover. (thanks @LeviRocks)
Pretty much the echo is an object and does not have any senses, so it cannot be blinded. If the Fighter cannot see the enemy at all, then it can't attack it. Even if right in front of the Echo. The only time the Fighter can see through the Echo is using the 7th level Echo Avatar ability. Using the Echo sort of like a wizard's familiar you can see and hear through it up to 1000' away. But you cannot attack through it while using this ability.
My DM has been kind to me though. I chose Blind Fighting as my PC's Fighting Style. And he's allowed it to work when the echo was in darkness and not the Fighter. But RAW, it should not work.
A lot of these things can be DM dependent, but the word "you" (as in, the Knight themselves) does a lot of the heavy lifting in many of the Echo Knight features. Specific to the teleport switch, and taking a party member along with you, by RAW the rule reads as:
" As a bonus action you can teleport, magically swapping places with your echo at a cost of 15 ft. of your movement, regardless of the distance between the two of you. "
To me, as per RAW, this clearly implies that the switch is solely between yourself, and your Echo.
That said, an unconscious party member is technically an object, if memory serves. So, I could probably be convinced to allow it in a particularly relevant or dramatic moment; despite going against my own reading of RAW.
For RAI, your own mileage may vary depending on your particular DM and table, though I would argue that any DM would be quite generous to allow it. Even if the feature itself doesn't explicitly preclude the carrying of a human-sized object, for RAI, the Echo Knight's Echo/Teleport feature seems to share more similarities with spells like Misty Step, rather than say, Dimension Door.
EDIT: Elaborated on previous detail and added Beyond reference to feature quote.
Another scenario maybe covered sorry if I missed it.
A party member was down, I picked them up and then did the switch teleport. I could not see anywhere saying you can't do this?
The definition of teleportation in the 2024 Player's Handbook says that "if you're touching another creature when you teleport, that creature doesn't teleport with you unless the teleportation effect says otherwise", so it doesn't work under 2024 rules as written.
The 2014 rules lack a detailed definition of teleportation like this, but the fact that some teleportation effects (e.g. Dimension Door) explicitly say you can bring someone else along with you argues that that's not allowed with effects that don't explicitly say it is.
This may have been answered earlier but I didn't see it so...
Can the echo move in any way if the fighter doesn't command it to do so?
Also, if the fighter knows Common Sign Language from 2024 rules, could the fighter instruct their echo use it too?
If the answer is yes to both of those questions, here's another:
Can the echo communicate its own opinions/thoughts/observations through Common Sign Language?
I would say no to moving without command from the fighter, and communicating opinions. It is not an entity in itself, it is a "shadow", a remnant of possible version of yourself. It can only do attacks, and the attacks are from the fighter.
This may have been answered earlier but I didn't see it so...
Can the echo move in any way if the fighter doesn't command it to do so?
Also, if the fighter knows Common Sign Language from 2024 rules, could the fighter instruct their echo use it too?
If the answer is yes to both of those questions, here's another:
Can the echo communicate its own opinions/thoughts/observations through Common Sign Language?
What an interesting idea to use your echo for communication or allowing it to communicate or move as an independent entity As SlowestCat mentioned, this isn’t supposed by RAW. But this is certainly something you should discuss with your DM I’ve had a number of ideas for “Echos” that where similar.
For example, one concept I had was that the echo was actually my knight’s figurative shadow, their darker half. It had its own mind and would sometimes move about while my knight was asleep. Or act on its own in combat, such as choosing to kill its target instead of sparring the enemy as the knight wished. But this can all be done through roleplaying, while still keeping within the rules. I could say the echo is moving of its own accord against the knights will, but it is still using the knights action/turn to do it. If you do wish to give it a degree of independence, I would just suggest that it shouldn’t give you added advantaged in combat. Or you could even give control to the DM if it moved or acted independently as if it were half an NPC. Ultimately this would of course be a call for your DM. But I do love your creativity thinking.
I personally think the rules are primarily there for balance, but roleplaying-wise you can flavor them however you want and think outside the box description.
Since the Echo Knight attacks as if it were in the echo's space, something like Darkness would impart the Blinded condition.
These are the two questions from the start of this thread that can give some insight into your question. Can't change the numbers here, but they are actually #12 & 13 from the Attack section.
A: No by RAW, because the Echo has no "senses" without you using the level 7 ability. Thus an Echo cannot help a Knight see her target. (thanks @LeviRocks)
A: No, because the attack would originate from a position that wouldn't have the cover. (thanks @LeviRocks)
Pretty much the echo is an object and does not have any senses, so it cannot be blinded. If the Fighter cannot see the enemy at all, then it can't attack it. Even if right in front of the Echo. The only time the Fighter can see through the Echo is using the 7th level Echo Avatar ability. Using the Echo sort of like a wizard's familiar you can see and hear through it up to 1000' away. But you cannot attack through it while using this ability.
My DM has been kind to me though. I chose Blind Fighting as my PC's Fighting Style. And he's allowed it to work when the echo was in darkness and not the Fighter. But RAW, it should not work.
Another scenario maybe covered sorry if I missed it.
A party member was down, I picked them up and then did the switch teleport. I could not see anywhere saying you can't do this?
A lot of these things can be DM dependent, but the word "you" (as in, the Knight themselves) does a lot of the heavy lifting in many of the Echo Knight features. Specific to the teleport switch, and taking a party member along with you, by RAW the rule reads as:
To me, as per RAW, this clearly implies that the switch is solely between yourself, and your Echo.
That said, an unconscious party member is technically an object, if memory serves. So, I could probably be convinced to allow it in a particularly relevant or dramatic moment; despite going against my own reading of RAW.
For RAI, your own mileage may vary depending on your particular DM and table, though I would argue that any DM would be quite generous to allow it. Even if the feature itself doesn't explicitly preclude the carrying of a human-sized object, for RAI, the Echo Knight's Echo/Teleport feature seems to share more similarities with spells like Misty Step, rather than say, Dimension Door.
EDIT: Elaborated on previous detail and added Beyond reference to feature quote.
Frequently flippant; sorry for being an apologist.
The definition of teleportation in the 2024 Player's Handbook says that "if you're touching another creature when you teleport, that creature doesn't teleport with you unless the teleportation effect says otherwise", so it doesn't work under 2024 rules as written.
The 2014 rules lack a detailed definition of teleportation like this, but the fact that some teleportation effects (e.g. Dimension Door) explicitly say you can bring someone else along with you argues that that's not allowed with effects that don't explicitly say it is.
pronouns: he/she/they
This may have been answered earlier but I didn't see it so...
Can the echo move in any way if the fighter doesn't command it to do so?
Also, if the fighter knows Common Sign Language from 2024 rules, could the fighter instruct their echo use it too?
If the answer is yes to both of those questions, here's another:
Can the echo communicate its own opinions/thoughts/observations through Common Sign Language?
I would say no to moving without command from the fighter, and communicating opinions. It is not an entity in itself, it is a "shadow", a remnant of possible version of yourself. It can only do attacks, and the attacks are from the fighter.
What an interesting idea to use your echo for communication or allowing it to communicate or move as an independent entity As SlowestCat mentioned, this isn’t supposed by RAW. But this is certainly something you should discuss with your DM I’ve had a number of ideas for “Echos” that where similar.
For example, one concept I had was that the echo was actually my knight’s figurative shadow, their darker half. It had its own mind and would sometimes move about while my knight was asleep. Or act on its own in combat, such as choosing to kill its target instead of sparring the enemy as the knight wished. But this can all be done through roleplaying, while still keeping within the rules. I could say the echo is moving of its own accord against the knights will, but it is still using the knights action/turn to do it. If you do wish to give it a degree of independence, I would just suggest that it shouldn’t give you added advantaged in combat. Or you could even give control to the DM if it moved or acted independently as if it were half an NPC. Ultimately this would of course be a call for your DM. But I do love your creativity thinking.
I personally think the rules are primarily there for balance, but roleplaying-wise you can flavor them however you want and think outside the box description.