Nightmare Reshiram is Reshiram's Nightmare form, from the Nightmare World: darker, with 20% more health and move damage than a normal Reshiram, and able to grow all the way to level 999.
Awakening a Reshiram
Raise a Reshiram to 5★ and level 100, then Awaken it from its details window with 10 Nightmare Shards and 100,000 gold. It becomes Nightmare Reshiram (rank ☾1, level cap 200), and its Nightmare ranks take it up to 999.
Nightmare Reshiram doesn't defend any map of the Nightmare World: Awakening is the way to get one.
What changes
- It keeps its genes, moves, traits and held item; holding its Mega Stone, it becomes a Nightmare Mega.
- It wears no costume.
- In the Arena it fights at level 100 at most, with a normal form's stats.
- A shiny can't become a Nightmare form: it Ascends instead.