Heroes of Might and Magic III: In the Wake of Gods is a massive modification of HMMIII inventing script language and generally intended to stretch the boundaries of the original game capabilities. HMMIII WoG presents new objects with various properties, drastically changed and improved creature abilities and a wide variety of custom scripts for altering the gameplay.
The popular option for many HoMM3: WoG players - the Stack Experience allows every creature stack to earn its own experience points which affect its various statistics in a positive way. Like any other WoG option, this option can be enabled or disabled.