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1. Jelu is beneficial at the very beginning (especially since the starting army consists of snipers).
2. The dragon is more useful in the later stages of the game (as a wizard is better than snipers).
3. Sandro, although I like him as a hero (especially after the campaign in Shades of Darkness), doesn't really stand out.
4. Andrien is also only useful at the beginning.
5. Kreg Hack (although I also like him as a hero after Shades of Darkness) doesn't offer much... he has the same specialty as Gundula.
6. Xiron (maybe you meant Kseron?) If it's Xiron, then the Inferno specialty is also only beneficial at the beginning.
7. Mutare is useful in the later stages of the game, and only when commanding dragons.
8. The Cyclops specialty is not very good.
9. Jhem...
I voted for Katerina because I like the Crusaders (although the specialty isn't very good either).
Note about the poll:
1. There are many special heroes missing:
1) Kseron
2) Roland
3) Lord Haart (Knight)
4) Lord Haart (Death Knight)
5) Kilgor
6) Boragus