Guardian Angel - a special ability for the Human hero in Heroes of Might and Magic (although initially it was planned as a mentor). There can be no talk of any additional effects in battle (technically).

Why not? It could be - in the form of some kind of buff. For example, a built-in Regeneration. By the way, the Orc's special ability is simply "useless" because it just adds Fury points, which are also added by cities and Blood Memory. In my old modding experiments, I made Pure Fury a regular perk (naturally, reducing the Fury gain from 500 to 200). And I used General Support as the special ability. Which, indeed, looks creepy, especially under Krag.