Blackbeard's Yami Yami fruit is really different than most logias, mainly because it doesn't give you intangibility that can only be countered with armament haki or a elemental counter, for example, Crocodile would be severely weakened if water spills on him, he can be hit by Luffy's wet fists even without haki, Enel can be hit by Luffy since Luffy is rubber, but what if the Yami Yami Fruit actually posseses the Logia intangibility but is simply always under the effect of an elemental counter, since Blackbeard is Darkness, we can assume that he is countered by light.
If my theory is correct, Blackbeard can use the full potential of his fruit only if he is in a place devoid of light. I think Blackbeard's Yami Yami Fruit is part of the reason why he can absorb multiple devil fruits, but he can only do it when he is not weakened by light, that's why i think he covered Whitebeard in black cloth before absorbing his devil fruit, Blackbeard was not weakened while under the black cloth because it shielded him from the light.
If my theory is correct, Blackbeard can use the full potential of his fruit only if he is in a place devoid of light. I think Blackbeard's Yami Yami Fruit is part of the reason why he can absorb multiple devil fruits, but he can only do it when he is not weakened by light, that's why i think he covered Whitebeard in black cloth before absorbing his devil fruit, Blackbeard was not weakened while under the black cloth because it shielded him from the light.
