Third Generation Third Generation Slann use up an extra Hero choice (so they take up a Lord and a Hero choice).
In addition to any other spells, they also know Drain Magic spell.
And they have +1 wound.
However, Slann of the Third Generation are so ancient and revered that if one is killed in a game, the Lizardmen player's opponent gains 100 Victory Points added to his total at the end of the battle.