The Jem'Hadar have a reptilian appearance, with bluish-grey skin and vestigial horns. Due to extensive genetic engineering, they do not breed, eat, drink or sleep; they subsist entirely on Ketracel-white. Jem'Hadar are born in hatcheries and kept in stasis until they are deployed. Their development is extremely rapid, going from birth to adulthood in three days. Their average life expectancy is less than 20 years; no Jem'Hadar has lived to see 30.
Jem'Hadar possess a rudimentary cloaking ability known as a "shroud", which is capable of visually blending a Jem'Hadar in with his surroundings.
- "I am dead. As of this moment, we are all dead. We go into battle to reclaim our lives. This, we do gladly, for we are Jem'Hadar. Remember - victory is life."
- -- Jem'Hadar ritual pre-battle address
The Jem'Hadar are bred and conditioned to be what the Dominion considers "perfect soldiers". They are fanatically devoted to the Founders, whom they revere as gods; failure to adequately protect a Founder is seen as sufficient reason to commit suicide. Jem'Hadar have a rudimentary rank system based on seniority, although all Jem'Hadar are subordinate to the Vorta. Their only purpose in life is military service; because of this, they feel no need for entertainment or personal relations. Jem'Hadar often employ "human wave" attacks against enemy positions.
As the military force of the Dominion, the Jem'Hadar are generally both capable (by Star Trek standards) and disposable. A freshly hatched Jem'Hadar can be combat-ready in a matter of days, so the Dominion spends them casually in wars of attrition. Nonetheless, an individual Jem'Hadar soldier with only weeks of preparation is as capable as a Federation or Klingon soldier with months or years or training.
Jem'Hadar also provide naval personnel as crew for attack ships and Dominion battleships. As attack ships and their crews are easily replaceable, they are often used with an attrition strategy, using kamikaze attacks freely. The crews of the rarer Dominion battleships are not as reckless.
While dangerous in close combat, Jem'Hadar ferocity and recklessness are not likely to prevail against an enemy with comparable technology that uses combined-arms tactics unless they have a substantial numerical advantage. Similarly, Jem'Hadar are aggressive and dangerous opponents in space, but they do not fare well against adversaries that use comparable technology in a more balanced strategy unless they outnumber their opponents by a large margin.
- Sontarans: Another species of mass-produced cloned warriors, although one which is not subservient.