If I have The Ur-Dragon in the command zone, or other such cost reducing cards on the field, do I cast a dragon with Megamorph such asAcid-Spewer Dragon for 2 or fewer mana?
Only if you cast it face up. If you cast it face down, you put the card face down on the stack, the other players don't get to see what it is. The card will be a generic 2/2 creature spell with no name, no creature type, and no color, and since it is not a dragon spell while face down, the cost reduction of the Ur-Dragon doesn't apply.
If you have a cost reduction that can still apply to the face down spell, then it reduce the cost, for example if you have a cost reduction for creature spells or colorless spells.
No and no.
The Morph ability that allows you to cast the card face down for 3 mana, isn't affected by The Ur-Dragon cost reduction. As you aren't casting a dragon, you are casting a creature, that has no colour or creature type.
And equally, the ability to turn the morph creature face up, is just that an ability. You aren't casting the dragon. So the cost reduction isn't relevant, as that only applies to casting dragon spells.
If you cast a card face down with megamorph, you do so as a "creature with ... no subtypes" (C.R. 702.36b), so it won't count as a Dragon spell (C.R. 205.3m); therefore, The Ur-Dragon's cost reduction won't affect that.
Typelessness aside, how would any other player know that it's a dragon? It's face-down.
For the purpose of The Ur-Dragon's second ability, the face-down creature (after it's cast) will still have no subtypes, including Dragon; so still generally won't count as a Dragon (C.R. 707.2, 205.3m).
Typelessness aside, how would any other player know that it's a dragon? It's face-down.
For the purpose of The Ur-Dragon's second ability, the face-down creature (after it's cast) will still have no subtypes, including Dragon; so still generally won't count as a Dragon.
I know, I was just trying to figure out the OP's logic here. He tried to apply a cost reduction that needs public information by default to hidden information.
I know, I was just trying to figure out the OP's logic here. He tried to apply a cost reduction that needs public information by default to hidden information.
Under C.R. 707.2, "[f]ace-down spells ... have no characteristics other than those listed by the ability or rules that allowed the spell ... to be face down". Thus, for the purposes of The Ur-Dragon's cost reduction effect, the face-down card doesn't have any subtypes (including Dragon) because the megamorph ability says it doesn't (C.R. 702.36b, 203.5m).
If you have a cost reduction that can still apply to the face down spell, then it reduce the cost, for example if you have a cost reduction for creature spells or colorless spells.
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The Morph ability that allows you to cast the card face down for 3 mana, isn't affected by The Ur-Dragon cost reduction. As you aren't casting a dragon, you are casting a creature, that has no colour or creature type.
And equally, the ability to turn the morph creature face up, is just that an ability. You aren't casting the dragon. So the cost reduction isn't relevant, as that only applies to casting dragon spells.
Hope that helps.
I know, I was just trying to figure out the OP's logic here. He tried to apply a cost reduction that needs public information by default to hidden information.