The paladin is not a wizard, warrior, priest, or thief, but he possesses the abilities of each. That means Vampires can attack him (he is not a priest). An Anti-magic Dart has no special effect if it hits him (he is neither a priest nor a wizard), but if it hits a wizard or priest it does prevent the paladin from casting spells or healing.

The paladin is still an adventurer, so anything that affects adventurers affects him (including traps and attacks that damage all adventurers).

The paladin goes first (except when Illusion was cast), so all standard attacks have to target him, and ghosts can’t attack him. Rolling Stone and Poisoned Meal affect the paladin, while the Pendulum hits the first adventurer behind him.