1. If Merfolk Trickster use it's etb ability targeting Mist-Cloaked Herald , can i block mist-cloaked herald
I got confused because of this
112.12 An effect that sets an object’s characteristic, or simply states a quality of that object, is different from an ability granted by an effect. When an object “gains” or “has” an ability, that ability can be removed by another effect. If an effect defines a characteristic of the object (“[permanent] is [characteristic value]”), it’s not granting an ability. (See rule 604.3.) Similarly, if an effect states a quality of that object (“[creature] can’t be blocked,” for example), it’s neither granting an ability nor setting a characteristic.
Example: Muraganda Petroglyphs reads, “Creatures with no abilities get +2/+2.” A Runeclaw Bear (a creature with no abilities) enchanted by an Aura that says “Enchanted creature has flying” would not get +2/+2. A Runeclaw Bear enchanted by an Aura that says “Enchanted creature is red” or “Enchanted creature can’t be blocked” would get +2/+2.
112.12 deals with abilities and characteristics granted onto permanents by other effects, so it doesn't have anything to do with how Merfolk Trickster works when dealing with creatures that innately cannot be blocked. If you flash it in while Mist-Cloaked Herald is attacking and target the herald with the ability, you will be able to block the herald.
It is true that a flashed-in Trickster will be able to block Herald, but I disagree with BlazingRagnarok's comment.
Rule 112.12 is totally relevant here.
First, nowhere is it mentioned that ''112.12 deals with abilities and characteristics granted onto permanents by other effects'', so this pretence can readily be dismissed.
Second, Mist-Cloaked Herald's ability fits EXACTLY with the example provided by 112.12: “[creature] can’t be blocked,”
Now, let's focus on 112.12's essential parts: 112.12. An effect (…) is different from an ability granted by an effect.
OK: an effect cannot be removed the same way an ability can, because they are different things. Got it.
Therefore, we cannot easily remove the effect ''Mist-Cloaked Herald can't be blocked.''
But where does that effect comes from?
It comes from Mist-Cloaked Herald's static ability:
112.3d Static abilities are written as statements. They’re simply true. Static abilities create continuous effects (…)
So, what happens when Merfolk Trickster removes the ability? What becomes of the effect?
112.3d (...) Static abilities create continuous effects which are active while the permanent (…) has the ability (…)
The 'unremovable' effect CEASED to be active as soon as we removed the ability creating it.
Removing the ability erased the effect, because it is a static ability: it needs to be there to create its effect.
The confusion here probably comes rom the fact that both the effect and the ability use the exact same words: ''Mist-Cloaked Herald can't be blocked.''
(note that things would be different with a card like Amphin Pathmage, because of rules 112.3b & 611.2a)
I got confused because of this
112.12 An effect that sets an object’s characteristic, or simply states a quality of that object, is different from an ability granted by an effect. When an object “gains” or “has” an ability, that ability can be removed by another effect. If an effect defines a characteristic of the object (“[permanent] is [characteristic value]”), it’s not granting an ability. (See rule 604.3.) Similarly, if an effect states a quality of that object (“[creature] can’t be blocked,” for example), it’s neither granting an ability nor setting a characteristic.
Example: Muraganda Petroglyphs reads, “Creatures with no abilities get +2/+2.” A Runeclaw Bear (a creature with no abilities) enchanted by an Aura that says “Enchanted creature has flying” would not get +2/+2. A Runeclaw Bear enchanted by an Aura that says “Enchanted creature is red” or “Enchanted creature can’t be blocked” would get +2/+2.
Rule 112.12 is totally relevant here.
First, nowhere is it mentioned that ''112.12 deals with abilities and characteristics granted onto permanents by other effects'', so this pretence can readily be dismissed.
Second, Mist-Cloaked Herald's ability fits EXACTLY with the example provided by 112.12: “[creature] can’t be blocked,”
Now, let's focus on 112.12's essential parts: 112.12. An effect (…) is different from an ability granted by an effect.
OK: an effect cannot be removed the same way an ability can, because they are different things. Got it.
Therefore, we cannot easily remove the effect ''Mist-Cloaked Herald can't be blocked.''
But where does that effect comes from?
It comes from Mist-Cloaked Herald's static ability:
So, what happens when Merfolk Trickster removes the ability? What becomes of the effect?
The 'unremovable' effect CEASED to be active as soon as we removed the ability creating it.
Removing the ability erased the effect, because it is a static ability: it needs to be there to create its effect.
The confusion here probably comes rom the fact that both the effect and the ability use the exact same words: ''Mist-Cloaked Herald can't be blocked.''
(note that things would be different with a card like Amphin Pathmage, because of rules 112.3b & 611.2a)
RULES OF MAGIC :
http://magic.wizards.com/en/game-info/gameplay/rules-and-formats/rules