The acid blob, b, is an amoeboid monster in NetHack. It is the first acidic monster most players will encounter, and also likely the first amorphous monster as well. Acid blobs do no damage on their own, buthave an acid-splashing passive attack that can corrode weapons and armor.
Acid blob corpses are unique in that they are always fit for sacrifice, and do not become tainted from aging similar to lichen and lizard corpses, though they can still rot away. Eating an acid blob corpse will do 1d15 damage unless you are acid resistant; a tin of acid blob will not do any damage. Acid blob corpses are considered vegan-friendly.
Acid blobs will act the same as any other hostile monster, but are ultimately harmless; however, attacking them poses a threat to an inexperienced and/or low-level player, and their amorphous forms allow them to ooze under doors and block a player's path.
For some early characters, it is best to dispatch them at a distance with disposable projectiles like rocks or non-iron projectiles, such as elven daggers. Wands and spells can work, but are better saved for more direct threats. If you have enough HP to survive a few splashes of acid, then use a disposable/non-iron weapon, attack bare-handed or simply kick them; the acid splash may still affect any non-corrodeproof iron armor. Past this point, acid blobs are little more than a nuisance that can occasionally erode weapons and armor if a player is careless in dispatching them, and even that annoyance is easily dealt with using corrode-proofed weapons and armor.
Acid blob corpses have value both as long-lasting sacrifice fodder and a means of curing stoning; acid blob tins can also cure stoning without dealing acid damage, but may take too long to safely open unless blessed.
Later in the game, players may employ confused readings of scrolls of create monster to fill up a dungeon level with acid blobs and prevent other monsters from reviving; this is a common method to take care of the Riders on the Astral Plane.
These giant amoeboid creatures look like nothing more than
puddles of slime, but they both live and move, feeding on
metal or wood as well as the occasional dungeon explorer to
supplement their diet.
But we were not on a station platform. We were on the track ahead
as the nightmare, plastic column of fetid black iridescence oozed
tightly onward through its fifteen-foot sinus, gathering unholy
speed and driving before it a spiral, re-thickening cloud of the
pallid abyss vapor. It was a terrible, indescribable thing vaster
than any subway train -- a shapeless congeries of protoplasmic
bubbles, faintly self-luminous, and with myriads of temporary eyes
forming and unforming as pustules of greenish light all over the
tunnel-filling front that bore down upon us, crushing the frantic
penguins and slithering over the glistening floor that it and its
kind had swept so evilly free of all litter.