"Army slots" are the bottom 3 slots in each build. They are awarded from successful dungeon completions and every leader has a distinct pool of options. Each slot can be changed after unlocking by spending Arclight Energy.
Sylvanas attacks with unrelenting arrow shots, and releases a Banshee when she dies.
All and Minis gain 30% movement speed near Sylvanas.
Pierce through enemies in a line, dealing Elemental damage.
Scream on Death, Stunning nearby enemies for 3 seconds.
Nearby Horde and Undead Minis gain Fury.