Board Thread:Questions and Answers/@comment-28154750-20160412005155

I was looking through my new hollow black dragon trial deck and wondered something, if a monster has an ability based on drop zone cards and doesn't say when enters the field, like f it says "if there are five or more cards in your opponents drop zone the card gets double attack" can the ability kick in when ever requirements are met(the monster currently being in play) or this ability can only happen if there are five or more when it comes in? (My question comes from the Twin Blade Dragon,Zalcandira card) 