Rocs and Thunderbirds are the level 5 creatures of Stronghold. They are recruited from the Cliff Nest.
"Rocs and thunderbirds are the only flying units available at Stronghold towns. When thunderbirds attack, there is a 20% chance thunderbolts will strike their target, delivering 10x the number of attacking thunderbirds in additional damage." RoE manual
Lightning strike special ability
Thunderbirds have special ability lightning strike, which has 20% probability to occur after the stack have attacked, including retaliations. When the stack attacks, the lightning strike occurs before the enemy has a chance to retaliate. If successful, the lightning strike deals additional damage for the amount of ten times the number of attacking Thunderbirds. The thunderbolts have the same visual effect as the spell Lightning Bolt, and the special attack is also counted as one in terms of immunities and Golems' spell damage resistance (e.g. if 14 Thunderbirds attack a stack of Diamond Golems with a lightning strike, they will do 7 damage instead of 140 because Diamond Golems have 95% spell damage resistance).
Heroes with a specialty
Shiva the Barbarian has rocs as a specialty, which increases the attack and defense skills of any rocs or thunderbirds for each level attained after 5th level and gives them a speed bonus of 1.
See also: