Looking for opinions from other DM's of this encounter.
The party must face a 'mirrored' version of themselves. Each mirror has the same HP, AC, spells, equipment etc, and the encounter plays such that the mirror version of the character takes its turn in the initiative immediately after the original version of the character. The mirror versions would still have to roll the dice for their attacks and spells as usual, rather than copying what the player rolls.
Would such an encounter likely fall more to strategy or luck? What do other DM's suggest for changes?
I think you need to build more lore into this encounter. Why are there mirror characters? Is it a deity's illusion? The way the mirrored characters may behave greatly depends on their motive and purpose. As for the encounter itself, it might be difficult to keep track of. You need to know your players well, and D&D Beyond's Combat Tracker doesn't have the ability to fight players. Aside from all of that, it is probably a relatively balanced encounter.
It depends on what is on the map. If the environment has terrain and objects the players can utilize and interact with, then strategy can come into play. Also to keep in mind is that the players may have consumables where the mirrored probably won't. Another factor you can add in to tip the balance to players is to have the mirror versions target specifically their original, the mirrors don't work as a team, they're each focused on their target. Whereas the players can work as a team, using abilities and spells and against different mirrored.
My favourite version of mirrored encounter is based on the original Tomb Raider. The mirror version’s primary purpose is to block the path ahead and make actions at the exact same time as the original.
The trick to defeat it is to realise that the map is not perfectly symmetrical and you cannot fight the mirror version head on, but can lead it to the trap that is on their side but not yours.
I like your version as well, might be a quite random encounter depending on the rolls a lot but PCs starting each round first should allow them to win if they do not act exceptionally stupid.
Characters are not mathematically built to fight other characters. The AC vs. to hit bonuses vs. damage they do is calibrated against monsters, not other PCs. A fight like this is going to come down more to who has lucky rolls than anything else, and it will be pretty risky for the PCs if either you have a hot hand, or they have an unlucky session.
You might have better luck designing a CR appropriate encounter with regular monsters, then re-skinning them so they look like the PCs.
I’ll have to agree with Xalthu. Unless you reskin some existing monsters and maybe add a couple traits/abilities that your PCs posses, this would likely be a battle of luck.
One thing I’ve done that worked well was to have my party fight undead versions of themselves. I simply grabbed some undead monsters with their typical undead abilities and added one PC species ability and one PC subclass ability.
Without the PCs knowledge, copies were created by a Hag coven who got ahold of their hair/blood and over time cast simulacrum. They then ate the copies and reanimated them. The PCs had a mental connection to their copies and had nightmares with visions of their demise. It was fun watching them piece together meeting odd/friendly old ladies (they met weeks ago) to the horrible nightmares to meeting their undead copies.
Looking for opinions from other DM's of this encounter.
The party must face a 'mirrored' version of themselves. Each mirror has the same HP, AC, spells, equipment etc, and the encounter plays such that the mirror version of the character takes its turn in the initiative immediately after the original version of the character. The mirror versions would still have to roll the dice for their attacks and spells as usual, rather than copying what the player rolls.
Would such an encounter likely fall more to strategy or luck? What do other DM's suggest for changes?
I think you need to build more lore into this encounter. Why are there mirror characters? Is it a deity's illusion? The way the mirrored characters may behave greatly depends on their motive and purpose. As for the encounter itself, it might be difficult to keep track of. You need to know your players well, and D&D Beyond's Combat Tracker doesn't have the ability to fight players. Aside from all of that, it is probably a relatively balanced encounter.
If anybody would like my GMing playlists
battles: https://open.spotify.com/playlist/2mRp57MBAz9ZsVpw895IzZ?si=243bee43442a4703
exploration: https://open.spotify.com/playlist/0qk0aKm5yI4K6VrlcaKrDj?si=81057bef509043f3
town/tavern: https://open.spotify.com/playlist/49JSv1kK0bUyQ9LVpKmZlr?si=a88b1dd9bab54111
character deaths: https://open.spotify.com/playlist/6k7WhylJEjSqWC0pBuAtFD?si=3e897fa2a2dd469e
It depends on what is on the map. If the environment has terrain and objects the players can utilize and interact with, then strategy can come into play. Also to keep in mind is that the players may have consumables where the mirrored probably won't. Another factor you can add in to tip the balance to players is to have the mirror versions target specifically their original, the mirrors don't work as a team, they're each focused on their target. Whereas the players can work as a team, using abilities and spells and against different mirrored.
My favourite version of mirrored encounter is based on the original Tomb Raider. The mirror version’s primary purpose is to block the path ahead and make actions at the exact same time as the original.
The trick to defeat it is to realise that the map is not perfectly symmetrical and you cannot fight the mirror version head on, but can lead it to the trap that is on their side but not yours.
I like your version as well, might be a quite random encounter depending on the rolls a lot but PCs starting each round first should allow them to win if they do not act exceptionally stupid.
Characters are not mathematically built to fight other characters. The AC vs. to hit bonuses vs. damage they do is calibrated against monsters, not other PCs. A fight like this is going to come down more to who has lucky rolls than anything else, and it will be pretty risky for the PCs if either you have a hot hand, or they have an unlucky session.
You might have better luck designing a CR appropriate encounter with regular monsters, then re-skinning them so they look like the PCs.
I’ll have to agree with Xalthu. Unless you reskin some existing monsters and maybe add a couple traits/abilities that your PCs posses, this would likely be a battle of luck.
One thing I’ve done that worked well was to have my party fight undead versions of themselves. I simply grabbed some undead monsters with their typical undead abilities and added one PC species ability and one PC subclass ability.
Without the PCs knowledge, copies were created by a Hag coven who got ahold of their hair/blood and over time cast simulacrum. They then ate the copies and reanimated them. The PCs had a mental connection to their copies and had nightmares with visions of their demise. It was fun watching them piece together meeting odd/friendly old ladies (they met weeks ago) to the horrible nightmares to meeting their undead copies.