The player does not have to actually recruit Pent in Fire Emblem, but Pent must be protected in Chapter 22: Living Legend part of the game. After Pent is protected during Chapter 22, he automatically becomes part of the player's team and becomes available in Chapter 24: Unfulfilled Heart, along with another new character, Louise.
The main objective in Chapter 22 is to defeat all enemies. Several items can also be obtained on this map and these include Luna, Ocean Seal, Body Ring, Filla's Might, Eclipse, Light Rune and Hero Crest. Since this is a sand map, some of the items are buried in the sand. To retrieve the buried items, place a thief on a square where the buried items are located.
All the player's land units will move slower on this map, therefore it will be a good idea to send a flier to rescue Pent and get him out. Although, Pent does not really need help, he uses up experience that the player can really make use of on side quests.
On Chapter 24: Unfulfilled Heart, Pent becomes part of the player's team as a level 6 Sage. He has 33 Hit Points, 18 Strength, 21 Skill, 17 Speed, 14 Luck, 11 Defense and 16 Resistance. He is the second sage that the player can get on his team after Erk.