The Wildcat (stage 5) and the Stormcloud Sorcerer (stage 13) fight on their own.
Only in some modes
The stage heroes fight in Campaign and Classic Rush; Lord Blackburn and Prince Denas also fight in Iron Challenge. Blitz Challenge, Spell Rush and Hero Party are played without them.
Alleria
Stage hero, stage 5. Silveroak Village. 160 health, 8-13 physical damage.
Wildcat
Summoned unit, stage 5. Silveroak Village. 80 health, 6-9 physical damage.
Stormcloud Sorcerer
Stage soldier, stage 13. Stormcloud Halls. 120 health, 4-6 physical damage.
Lord Blackburn
Stage hero, stage 15. Castle Blackburn. 450 health, 26-40 physical damage.
Prince Denas
Stage hero, stage 18. Vez'nan's Tower. 750 health, 35-50 physical damage.