In the 10th Age, many slimes and jellies may be produced from an arcane process that was once common knowledge, but since the days of the great Mannish Schools and the Elvish Sorcerers passed has been lost. Individual wizards have rediscovered some of the principles of this hideous creation, known by arcanists as the mater limus, the Mother of Slime. This engineered liquid is produced by a series of as-yet still mysterious spells and enchantments performed on captured versions of the slimes, oozes, and jellies which one seeks to produce. These creatures are classically grouped amongst the accidental creations of Ulagos the Potter (legend has it that they were spawned from the mud thrown from his wheel while he was making his other nasty children). However that may be, the presence of a mater limus is a highly dangerous one.
They can be controlled by adding various reagents to their composition; vinegar will kill them (as will any sufficiently caustic fluid), while extracts of black puddings will simply cause them to sink into a hibernative period, requiring resuscitation with alchemical soda or niter.
Mater limus are of varying powers depending on the wizard who created them. Their shared traits, however are that:
...they possess no external membrane to protect themselves from other fluids, nor do they have any cohesion, meaning they must be stored in a well or container of some kind.
...they may spawn a number of "children" slime types, depending on how they were made.
...they may be in "active" or "inactive" states.
...they are non-sentient but living.
...they cannot move or propel themselves and generally have no attack form.
...they never spawn more than a few slimes or oozes every hour.
...they need to be fed extremely large meals once or twice a decade, but otherwise will continue to live and produce slimes without interaction or checks.
...lightning or other electricity generally causes them to divide and bud off new slimes immediately, losing a portion of their mass.