A is for Alphas, a special breed of Jem'Hadar bred in the Gamma Quadrant during the Dominion War.
B is for Born to fight, which is true of the Jem'Hadar
C is for the Conquering Dominion. Hail to them!
D is for Dominion, the ruling power in the Gamma Quadrant
E is for Enabran Tain, who was captured and held prisoner in a Dominion internment camp located inside the Gamma Quadrant
F is for Freaky shape-shifting aliens.
G is for Gods, which the Vorta and Jem'Hadar believed the Founders to be. Well, at the very least they treated them like gods.
H is for Heaven. To get to the Gamma Quadrant from the Alpha, you have to go through Bajoran heaven.
I is for IKS Rotarran, General Martok's ship that got several victories against the Jem'Heddar in the Gamma Quadrant.
J is for the Jem'Hadar, one of the most well trained and lethal warrior races in the known galaxy and genetically engineered inside the Gamma Quadrant.
K is for Ketracel-White. The drug that is the Jem'Hadar's weakness.
L is for Liquid state, the natural state of the Founders
M is for Martok. Scourge of the Dominion.
N is for Nog who served on the USS Defiant in the Dominion War.
O is for Odo, a Founder changeling who originated in the Gamma Quadrant before being discovered in our own part of the galaxy.
P is for Prophets, the entities living in the Wormhole that once defended the alpha-quadrant from the Fleet of Jem'Heddar ships in the Gamma Quadrant.
Q is for Quark, who once led a trade mission into the Gamma Quadrant that was the source of the Federation's first-ever information on the mysterious power known only as the Dominion.
R is for Remata'Klan, the BAMF of the Gamma Quad.
EDIT: I realized I made a horrible blunder.