R, 60

x=rbind(97:122-diag(26)*32,10)
cat(intToUtf8(c(x,x[,25:1])))

This is based on ASCII codes that are transformed to characters.

R, 60 59

cat(intToUtf8(c(x<-rbind(97:122-diag(26)*32,10),x[,25:1])))

Improvement based on the comment by @JayCe.

Former version:

x=rbind(97:122-diag(26)*32,10)
cat(intToUtf8(c(x,x[,25:1])))

This is based on ASCII codes that are transformed to characters.