The Frozen River

After defeating Arcard, Roy moved east deep into the frozen lands of Ilia.

''Soon, they entered the thick forests that characterize Ilia's central land. However, a general of Bern, Bishop Martel, was waiting for them with an ancient spell that was said to have been lost centuries ago...''

Chapter Info
The Frozen River is chapter 18 of Fire Emblem: Fūin no Tsurugi if you take the Ilian route (which happens if by the end of chapter 16, the experience points gained by Thany and Tate were more than that of Sue and Shin).
 * Boss:Martel
 * Villages (3):Secret Book, Goddess Icon and a Guiding Ring

Enemy Reinforcements

 * Turn: 6 : 1 Bandit from north, 1 Bandit from east
 * Turn: 7 : 1 Bandit from north, 1 Bandit from east
 * Turn: 8 : 1 Bandit from north, 1 Bandit from east
 * Turn: 9 : 1 Bandit from north, 1 Bandit from east
 * Turn: 10 : 1 Bandit from north, 1 Bandit from east
 * Turn: 11 : 2 Pegasus Knights from north
 * Turn: 12 : 2 Pegasus Knights from east
 * Turn: 13 : 2 Pegasus Knights from north
 * Turn: 14 : 2 Pegasus Knights from east
 * Turn: 15 : 2 Pegasus Knights from north
 * Turn: 16 : 2 Pegasus Knights from east
 * Turn: 17 : 2 Pegasus Knights from north
 * Turn: 18 : 2 Pegasus Knights from east