The Ur-Dragon says "you may put a permanent card from your hand onto the battlefield." This is not the same as a card like Etali, Primal Storm, which says "you may cast any number of nonland cards exiled this way without paying their mana costs." The Ur-Dragon's ability does not let you cast anything, so Nikya of the Old Ways doesn't interfere.
The Ur-Dragon's ability does not let you cast anything, so Nikya of the Old Ways doesn't interfere.
2023 Average Peasant Cube|and Discussion
Because I have more decks than fit in a signature
Useful Resources:
MTGSalvation tags
EDHREC
ManabaseCrafter