Paying half of your Life Points is a cost to activate “Dark Magic Curtain”.

If you Normal Summon, Flip Summon, or Special Summon a monster during a turn, you cannot activate “Dark Magic Curtain” during the same turn. For example, if you Normal Summon a monster during your Main Phase 1 you would not be able to activate “Dark Magic Curtain” during your Main Phase 2.

You can Set a monster before or after activating “Dark Magic Curtain”. However, it is not possible to Special Summon monsters face-down, using cards like “The Shallow Grave”, after activating “Dark Magic Curtain”.

If the effect of “Cyber Jar” activates during the same turn you activated “Dark Magic Curtain”, you will not be able to Special Summon the Level 4 or lower monsters that you pick up from “Cyber Jar's” effect. The Level 4 or lower monsters that you pick up will be sent to the Graveyard instead of being Special Summoned.

If you Normal Summon, Flip Summon, or Special Summon a monster and the monster's Summon is negated (by “Horn of Heaven”, “Solemn Judgment”, etc.), you still cannot activate “Dark Magic Curtain” during the same turn.

If you activate “Dark Magic Curtain” to Special Summon “Dark Magician” and later in the turn another effect would cause you to Special Summon a monster, you will not be able to Special Summon the monster. For example, your “Insect Queen” would not be able to Special Summon an “Insect Monster Token” during your End Phase.

When you activate “Dark Magic Curtain”, you cannot chain cards like “Call of the Haunted” or “Ultimate Offering” because you cannot Normal Summon or Special Summon during the same turn. Also, you cannot activate cards like “Premature Burial” or “Monster Reborn” after activating “Dark Magic Curtain”.

You do not have to pay any Life Points to activate “Dark Magic Curtain” while you have “Spell Economics” face-up on your side of the field.

If you Chain “Serial Spell” to “Dark Magic Curtain”, the effect that prevents you from Normal Summoning, Flip Summoning, or Special Summoning for the remainder of the turn is still applied. When “Serial Spell” resolves it will Special Summon 1 “Dark Magician” from your Deck and it will apply the Summon-restriction, so when “Dark Magic Curtain's” effect tries to resolve its effect will disappear because you cannot Special Summon a monster.