Cursed Jar is a unique monster that gives 300 XP when defeated. It can be found on the road between Lohan and the Nest of Dragon. It can sometimes drop a Night Raid after defeated. It runs away as soon as it gets the chance to do so, so measures must be taken to kill it before it can run away.
Much like 00PARTS, it runs away as soon as it gets a chance, but cannot instantly KO players. It only takes 1 damage per basic attack. Strategies for killing Cursed Jar copied from the 00PARTS strategies.
The first and simplest way is to have a Magic Sig Stone in your inventory. Have one character attack Cursed Jar for 1 or 2 damage, then the following character throw the stone. After Cursed Jar has been blocked, attack it, and repeat the throwing of the stone once the effect wears off. Cursed Jar has only 4 HP, but each character only attacks for 1 damage point.
The second method is the fastest, but requires Sachets. A Sachet will automatically damage Cursed Jar for 10 HP, killing it instantly. This method is somewhat more difficult because of the farming method for Sachets. See Sachet for details.
On disc 3 it gets easier. Miranda, dancer's shoes, wargod's amulet, and long bow= impossible to miss. So use Miranda, Dart and Haschel (or Meru). First move, 'magic sig stone', second (unless miranda) - 'speed up' miranda, third (unless miranda) - 'slow down' Cursed Jar. Unless Cursed Jar starts with instakill/run= you WILL win. Miranda will get 4-7 attacks by herself: the other characters are just for some unnecessary cushion.
(As for all special monsters, it is recommended you find the Speed Up, Speed down, and Signet Stone repeatable items to help increase your odds of killing said monsters. Good luck.)