Hmm... I've to say that I do miss some speed-enhancing spell. When it comes to boost the current Haste so it both raise initative and speed, then I feel that you are talking about making Haste to a T3 or T4 spell.
Well, you see, when you cast the HOMM 5 one on a high initative unit, he will get more turns, and attack more then the opponent can retaliate.
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