“Dark Paladin” cannot be Special Summoned, EXCEPT by Fusion Summon. So you cannot Special Summon “Dark Paladin” using “Monster Reborn”, etc., even if he was properly Summoned before. You cannot Special Summon “Dark Paladin” using “Magical Scientist”, etc.
You can use “substitute” Fusion Material Monsters such as “Goddess With the Third Eye”, etc. to Fusion Summon “Dark Paladin”.
“Dark Paladin”’s Spell-negating effect is a Multi-Trigger Effect, so it can be activated during your opponent’s turn.
You can activate “Dark Paladin”’s Spell-negating effect multiple times in the same chain.
“Dark Paladin”’s Spell-negating effect can be chained to.
If you activate “Dark Paladin”’s Spell-negating effect, and your opponent chains “Ring of Destruction” to destroy “Dark Paladin”, the Spell Card is still negated even though “Dark Paladin” is destroyed.
If you activate “Dark Paladin”’s Spell-negating effect, and your opponent chains “Book of Moon” to flip “Dark Paladin” face-down, the Spell Card is still negated even though “Dark Paladin” is face-down.
“Dark Paladin”’s +500 ATK effect is a Continuous Effect. While “Skill Drain” is active, the effects of “Dark Paladin” are negated.
Netrep Rulings:
“Dark Paladin” may be summoned with the aid of Fusion Substitution Monsters like “Goddess with the Third Eye.”
The effect of “Dark Paladin” may be activated in the Damage Step.