Legacy Units are special units that have unique Skills that they can't normally get from normal game play. Such as Ephraim Legacy with Conquest Skill, Michaiah with Shadowgift Skill, and Katarina with Rally Strength. Below will explain each of the Legacy Unit's skills and where you can get them in normal game play. Also, like Phantom Units, Legacy Units can reclass into any classes you desire.
Pr. Marth (Lodestar) - Has Appitude Skill. It is a signature skill for Villager class. This gives Marth an additional 10% to his growth rates.
Est (Pegasus Knight) - Has Appitude & Luck +4 Skills. Luck +4 is a signature skill for Dancer class. It gives a bonus stat to Luck by 4 points.
Catria (Dark Flier) - Nothing interesting about this Legacy Unit; possesses no illegitmate skills or class.
Palla (Falcon Knight) - Has Counter & Rally Strength Skills. Both are male only skills from Warrior and Berserker classes. Both are explanatory.
Alm (Dread Fighter - You get him as the only playable Dread Fighter unit until you give a Dread Scroll to a male unit.
Celica (Sage) - Has Rightful King Skill. It is a skill exclusive to Great Lords. It is only passable to Chrom's son (even if he did not have this skill).
Seliph (Sword Master) - Has Galeforce Skill. It is a female only skill from Dark Flier class. This allows him to move again if he kills an enemy unit.
Eldigan (Paladin) - Has Charm Skill. It is a skill exclusive to Lord class. This grants Hit and Avoid by 10% to his allies within his 3-tile radius.
Leif (Trickster) - Has Underdog Skill. It is a skill exclusive to a Villager class. Grants Avoid & Hit by 15% if enemy level is higher (Lv.+20 if promoted).
Roy (Mercenary) - Has Dual Strike Skill. It is a skill exclusive to a Lord class. Grants an extra 10% chance of dual-striking if paired up.
Lyn (Sword Master) - Has Zeal Skill. It is a male only skill from a Fighter class. When HP is half or less, grants 5% Critical bonus.
Ephraim (Great Knight) - Has Conquest Skill; Walhart's signature skill as a Conqueror. It nulls bonus damage towards this user (Armor & Beast).
Eirika (Bride) - Is your only playable Bride (until Wedding Bouquet is given to a female unit) and has Luck +4 Skill.
Ike (Hero) - Has Aether Skill. Quite ironically, Ike is a Hero class in Radiant Dawn and is the only unit that uses this skill. Great Lords has this too.
Elincia (Falcon Knight) - Has Charm Skill. Refer to Eldigan for this skill.
Micaiah (Dark Mage) - Has Shadowgift Skill; Aversa's signature skill. It allows her to use Dark Tomes outside of Dark Mage classes.
Katarina (Grand Master) - Has Rally Strength & Shadowgift Skill. An overwhelmingly useful Legacy Unit, along with Micaiah.
|Pr. Marth||Complete [Champions of Yore 1] at least once|
|Roy||Complete [Champions of Yore 2] at least once|
|Micaiah||Complete [Champions of Yore 3] at least once|
|Leif||Complete [Lost Bloodlines 1] at least once|
|Alm||Complete [Lost Bloodlines 2] at least once|
|Seliph||Complete [Lost Bloodlines 3] at least once|
|Elincia||Complete [Smash Brethren 1] at least once|
|Eirika||Complete [Smash Brethren 2] at least once|
|Lyn||Complete [Smash Brethren 3] at least once|
|Ephraim||Complete [Rogues and Redeemers 1] at least once|
|Celica||Complete [Rogues and Redeemers 2] at least once|
|Ike||Complete [Rogues and Redeemers 3] at least once|
|Eldigan||Complete [Infinite Regalia] at least once|
|Est||Complete [Death's Embrace] at least once|
|Catria||Complete [Five-Anna Firefight] at least once|
|Palla||Complete [Roster Rescue] at least once|
|Katarina||Complete [Apotheosis] at least once|