"Heroes of Might and Magic II: The Succession Wars is a turn-based strategy video game developed by New World Computing and published in 1996 by the 3DO Company. The game is the second installment of the Heroes of Might and Magic series and is typically credited as the breakout game for the series. Heroes II was voted the sixth-best PC game of all time by PC Gamer in May 1997.
Heroes II introduced several new features that have since become standard for the series. First among them is the ability for heroes to gain special abilities. Each hero can possess up to eight different secondary skills out of fourteen available. Once gained, a skill can be developed from Basic to Advanced and Expert levels. For example, the Wisdom skill allows a hero to learn spells of level 3 and higher, while the Logistics skill increases the hero's movement ability over land. In Heroes I, heroes had a single fixed special ability according to their class.
The magic system was changed in Heroes II. Heroes I had used a memorization system in which each spell could be cast a certain number of times before being exhausted. Heroes II uses a magic point system that allows the player to apportion spell use as needed, while the varying point cost of different spells maintains balance.
Another major feature introduced in Heroes II is the ability to upgrade units, granting them improved statistics and, in some cases, important abilities. For example, upgrading Vampires to Vampire Lords enables them to absorb health and even to resurrect units."
Source: Wikipedia, "Heroes_of_Might_and_Magic_II:_The_Succession_Wars," available under the CC-BY-SA License.