From Dexella's official board posting:
Hardcore Heritage events have returned for 2016! We just wrapped up the increased challenges in Blackburrow and Cazic-Thule, and now it’s time to head to Lower Guk and Unrest!
For those who may have missed the events previously, Hardcore Heritage is a chance to revisit popular zones from classic EverQuest, but with a challenging twist! The zones are leveled up and the loot has improved.
Beginning on Wednesday, May 25, 2016, you will be able to venture into Darkened Ruins of Old Guk (Lower Guk) and Greater Unrest (Unrest). Undead frogloks and more have returned to take on adventurers who are leveled up to 85. Gear up and get ready for your adventure, but hurry! These events only last a limited time, and the zones will return to normal on June 8, 2016 at 11PM PDT.
Want more information? Visit Fanra’s wiki!
Taken from Fanra's impressive wiki:
Look forward to:
Wednesday, June 8 Crushbone a/k/a Clan Crushbone
Permafrost a/k/a Permafrost Caverns
90 Wednesday, June 22 Wednesday, June 22 Castle Mistmoore a/k/a The Castle of Mistmoore (Map)
Nagafen's Lair (Map)
100 Wednesday, July 20