Casting two copies of [Emrakul, the Promised End] does not give the opponent two extra turns.
According to this thread it occurs for a while: https://github.com/PennyDreadfulMTG/modo-bugs/issues/385
Recent example:
Awaken the Maelstrom (the Sorcery backside of the Invasion of Alara Battle) does not create a token copy of permanent controlled by its caster.
There is no prompt to select permanent to be copied at any time during the resolution of the spell.
Unverified - this might be related to not having...
According to the Mox Amber official rulings:
However, it is not possible to tap it to its own ability on Magic Online if you control no legendary creatures or planeswalkers, it is just inactive.
Sanctum Prelate did not stop a non-creature spell with {X} in the cost from being cast with the named total mana value
Sanctum Prelate was on the battlefield naming mana value 4
Opponent cast March of Otherworldly Light targeting the Sanctum Prelate with X = 3, total mana value 4 (notably no...