Dead Crusaders are particularly tough enemies that come armed with a sword and shield. They can either be skeletons or zombies depending on the game they appear in. They tend to raise their shields against almost all oncoming attacks, and even some that are not directly aimed at them. They are only vulnerable if caught unaware or whilst attacking.
Crusaders generally raise their shields when the player is at the same level as them and attacks, even if they are too far away. Attacks from above or below usually don't trigger them to start blocking. Likewise, attacks which are not directly aimed at them (i.e., the player is not facing at them) generally won't make them to start blocking either.
All variants drop the Blocking Mail, a chest armor piece which often nullifies any damage taken.
First appearance of the Dead Crusader in the series. It is a palette swap of the Skeleton Knight, albeit this time actually using the shield it holds to block attacks. They can be encountered in several areas of the castle, being particularly bothersome to deal with in areas where there are other enemies around, as they can provide them some level of protection.
They generally start blocking as the player performs an attack, although not always. Since most of their encounters happen in relatively close quarters, perhaps the best method to deal with them is just to attack continuously and hope one of these hits connects.
The Dead Crusader returns in Dawn of Sorrow as a zombie instead of a skeleton. He wields a sword, heavy armor, and a massive shield that blocks all attacks and will not flinch unless he stops blocking. The only way to kill him is to either hit him from very far away or wait until he lifts his sword to strike. Using the Nunchakus or the Valmanway is really handy against this undead knight, since he cannot block their attacks.
Another method to defeat him easily consists in equipping a weapon that traces a wide arc around the player, like a great sword, axe, or hammer. Approach the crusader, quickly face the opposite direction and attack. The weapon will hit him as it arcs behind the player and the crusader won't block since the attack is not directly aimed at him.
The Dead Crusader in Portrait of Ruin is just a recolored version of the Dawn of Sorrow sprite, and as such, behaves exactly the same, so the same tactics to deal with him apply. Furthermore, due to the versatility Jonathan's sub-weaponry and Charlotte's magic spells provide, there are many more options to defeat them from a safe distance this time around, like throwing vials of Holy Water at him from an elevated platform, or simply performing a wide area-of-effect attack, like the Holy LightningDual Crush.