Continuing on Skill drain, we still have very subject.
Costs Versus / Conditions:
Effects are not applied on conditions negatos. Some examples of these types of effect are: Debris Dragon, Djinn Releaser of Rituals, Scrap Chimera and the like.
Other Rulings:
What creates more confusion and doubt about the effect of Skill Drain is activated when it is to maintain a malefic on the field, so now I'll talk a little about it.
Actually I'll put here what I found in yugioh.wikia:
Malefic: If "Skill Drain" is negating the effect "There can only be 1 face-up" Malefic "monster on the field." of a monster like "Malefic Blue-Eyes White Dragon" or "Malefic Red-Eyes B. Dragon" or "Malefic Stardust Dragon", then you still can not Special Summon a second "Malefic Blue-Eyes White Dragon", since its effect is while it is still active in the hand.
Malefic: Suppose you remove from play "Malefic Blue-Eyes White Dragon" with a card like "Interdimensional Matter Transporter", and then another Summon "Malefic Blue-Eyes White Dragon", all while "Skill Drain" is active. During the End Phase, even though the effect "There can only be 1 face-up" Malefic "monster on the field." of the "Malefic Blue-Eyes White Dragon" on the field is negated, that effect of the removed-from-play "Malefic Blue-Eyes White Dragon" is still active, so the removed-from-play "Malefic Blue-Eyes White Dragon "can not return to the field. Thus, the removed-from-play "Malefic Blue-Eyes White Dragon" is sent to the Graveyard.
Malefic: If the effect of a monster like "Malefic Blue-Eyes White Dragon" or "Malefic Red-Eyes B. Dragon" or "Malefic Stardust Dragon" is negated by an effect like "Skill Drain" or "Forbidden Chalice", then its effect Which Prevents your other monsters from attacking is negated Also, so you can attack with a monster other than "Malefic Blue-Eyes White Dragon".
Malefic: If the effect of a monster like "Malefic Blue-Eyes White Dragon" or "Malefic Red-Eyes B. Dragon" or "Malefic Stardust Dragon" is negated by an effect like "Skill Drain" or "Forbidden Chalice", then its effect "If there is no face-up Field Spell Card on the field, destroy this card." Also is negated. Thus, "Malefic Blue-Eyes White Dragon" will not be destroyed if the Field Spell Card is removed from being face-up on the field.
[color=orange]Well, I hope I have clarified a bit about it, if there are still questions, post here and I will answer.