Kingdom Hearts II
During the Battle of the 1000 Heartless in Hollow Bastion, Sora has to single-handedly defeat a thousand Heartless, many of which are Armored Knights. Later, during a face-off against Saïx, Sora is surrounded by a group of Armored Knights summoned by Saïx, who expects him to fight them and release the hearts contained inside them. It is then that Sora and company are dragged into the Realm of Darkness by Maleficent.
Armored Knights appear in the scene in the Hall of Empty Melodies, but do not appear in any other part of the world.
An Armored Knight, true to its name, is a very thin, humanoid Heartless clad from head to toe in black, grey, and silver armor. Its spherical, pitch-black head and glowing, yellow eyes are visible in its helmet, and there are two red spirals decorating its visor. It also carries a sword with a gold guard and handle. Its Heartless emblem is on its abdomen.
The Armored Knight's name is a direct reference to its appearance, which is reminiscent of armor-clad knights.
The Armored Knight has low HP and is not especially aggressive, however it always appears in groups. Smaller groups can be dealt with using Magnet or Thunder magic, however in the Battle of the 1000 Heartless it is more efficient to utilize its powerful Rising Sun Reaction Command. In Kingdom Hearts II Final Mix, Armored Knights are somewhat more dangerous due to having more powerful attacks, however Limit Form provides an easy way to take out many at once with Sonic Blade while replenishing HP in the process.
The Armored Knight will often use its Jump Rush attack against distant opponents, as well as counterattacking with Spin Rush, both of which will display its Reaction Command.
Kingdom Hearts 358/2 Days
Saïx is shown summoning a line of Armored Knights in the opening movie of Kingdom Hearts 358/2 Days.