The Hallow is one of the Terraria's biomes.
The Hallow in The Legend of Maxx
Despite the fact that that hard-mode was not (yet) activated on this world, the Hallow can be seen in the fourth panel of the Comic #128. This is, until now, the only appearance of it in the Comic. However, June has made many references to it being the source of the Dryads' power. In comic #210 June says that hallow was sealed away by naiad king Xyvareth with the Night's Edge.