Questing Beast
A stepping bastard of a boss mob that can be solved with a summoning cleric and a high CHA petrifying bard situation. There are two types: a quest token dropping beast (1-100 QT) and a rare artifact dropping beast. They are released throughout the uptime at random intervals. Build a world-walk to find them.
For more information, check out Uptime Quests.
The Questing Beasts have pretty much all the defender procs, step, pzar, entropy, reflect, etc.