The Underhand is a large skeletal hand enemy that emerges from the ground to attack players that would have been featured in the Fire Temple update. The Underhand was showcased, along with other upcoming Ninjago enemies, in the September-October 2011 issue of LEGO Club Magazine, which claimed that the Underhand attacks by emerging from underground but in doing so becomes vulnerable. However, following the announcement of LEGO Universe's closure, the Fire Temple world was canceled, and Underhands never appeared in-game other than Mythran spawnings.
LEGO Club Magazine description
Look for a black circle darting across the ground. The Underhand is hiding right there. You don’t want to bump fists with this baddie! Just before the Underhand pops up from its hole, jump out of the way and crack it across the knuckles with whatever weapon you’ve got handy!
On November 18, 2011 at about 4:00 PM EST in the Avant GardensSentinel Encampment on the United Kingdom Server (Storm Universe), the Underhand was spawned. The Underhand did not attack anyone, although it performed the attack animations. Its health bar went down three times before it was finally smashed by three players.