Here is a concept art of Pearlina the Mermaid with legs. I gotta admit the legs might be alittle too big or long. Not to mention I gotta work on her excited eyes too. I think Pearlina would not need to have a magic potion or elixir to give her legs. Instead, mermaids in Sagomithya naturally getting legs once they go on surface world as long as they dont go on small rock cliffs that are not comfortable for feet and legs to stand or sit on. Like in a poster of how Ariel from the Little Mermaid was sitting on a rock.