Mediator

Mediators are a type of Specialist that debuted in Disgaea 2: Cursed Memories and appear in every other game in the series prior to Disgaea 5. Initially they could only be found within legendary items, although after Disgaea 2 they can also spawn within commons and rares as well. The level cap for a single Mediator is 100, but this reportedly gives only a 70% chance for the desired effect to occur.

When a Mediator and at least two other subdued Specialists are present in an item, if at least one other slot is free, then entering the Item World of that item and progressing to Innocent Town may lead to the creation of an additional dual-stat Specialist. As the chance is random, it's prudent to use a Mr. Gency's Exit directly before attempting to enter the Town, thus allowing a chance to save and perhaps remove unwanted Specialists.

The potential combinations are:
 * ATK+HP = Muscleman
 * ATK+SPD = Sprinter
 * ATK+HIT = Sniper (Disgaea 2&3), Pugilist (Disgaea 4)
 * SPD+HIT = Sniper (Disgaea 4)
 * ATK+INT = Hard Worker
 * DEF+RES = Patient
 * INT+SP = Nerd

The newly-created Specialist will be un-subdued (except in Disgaea 4), and relatively low-level compared to its parents: starting at about 1% of their combined total. Creation of a dual-stat Specialist is hence impossible if the parent's total is too low.

Dual-stat Specialists are effectively twice as strong as regulars of the same level, adding their full bonus to both of their related stats. Unlike single-stat Specialists, however, they do not bestow any bonuses when Item Bosses are defeated.