I believe there are a few Siren roleplayers but I could be wrong. Most of the roleplayers here on RPC are on Balmung with sizable population on Gilgamesh and other servers such as Adamantoise, Jenova, etc. If you want to keep at searching for RP on Siren, check on tumblr, the official forums or on reddit.com/r/ffxiv
Otherwise, if you're looking for a -large- variety of RP, Balmung is available.
In regards to adherence to lore, it really depends on who you RP with.
I myself roleplay with the idea that if the lore makes it seem plausible, I may go with it and bendy. Others are very strict and will roleplay with the idea that it is very defined; if it's not present in the game then it's not possible. Even possible to add that even if it is in the game, the main character is [you] the singular Warrior of Light who is the special one and as such not indicative of general roleplay.
Others want to stay away from WoL and Echo roleplay while others embrace it. Really just depends on who you find.
Otherwise, if you're looking for a -large- variety of RP, Balmung is available.
In regards to adherence to lore, it really depends on who you RP with.
I myself roleplay with the idea that if the lore makes it seem plausible, I may go with it and bendy. Others are very strict and will roleplay with the idea that it is very defined; if it's not present in the game then it's not possible. Even possible to add that even if it is in the game, the main character is [you] the singular Warrior of Light who is the special one and as such not indicative of general roleplay.
Others want to stay away from WoL and Echo roleplay while others embrace it. Really just depends on who you find.
