No. Enc.: 1
Movement: 30' (10')
Armor Class: 9
Hit Dice: 3-18
Attacks: 1 (Spit)
Hoard Class: I
XP: See the XP table according to encounter HD. Yellow Jelly has 3 special abilities.
Resembling a big yellow jelly cube, 1 foot per HD in dimension, with darker yellow gas swirling inside these monsters are slow and usually lurk in dark places where escaping hastily is hard. Their only purpose of life is to grow bigger and bigger, as they don't possess intelligence, feelings or thoughts.
When Yellow Jelly attacks it spits its target with slime. Save versus Poison or Death or the character is immediately turned into a gasous form leaving its equipment and possession on a pile. In next 1d6 turns the Yellow Jelly has absorbed the gasous remainings of the character.
To grow larger (in HD) the Yellow Jelly needs to absorb as many living beings as his current Hit Dice are. When that requirement is met the Yellow Jelly grows both in dimension and HD.
Yellow Jelly takes only half damage of normal weapons, normal damage from magic and double damage from fire. If destroyed by fire (the finishing blow was fire) the Yellow Jelly rips apart and the gas inside it explodes dealing 1d8 x HD damage in a radius of 3' x HD.
Note: I had a dream about this monster last night and decided to write it down.