... I don't feel young anymore.

Other Canon Background

When the Dead do walk seek water's run,
for this the Dead will always shun.
Swift river's best or broadest lake
to ward the Dead and haven make.
If water fails thee, fire's thy friend,
if neither guards it will be thy end.

Mostly, the series is about a lineage of necromancers. But those who lay the Dead back to rest, rather than those who bring them back.

The series the crossover draws from is the Old Kingdom Trilogy, often called the Abhorsen trilogy by Garth Nix. There are two different countries, side by side; One of magic (the Old Kingdom), and the other of technology (Ancelstierre). The border is marked by a wall, a physical barrier as well as a magical one. It's purpose: to keep out the Dead and other creatures from the Old Kingdom, through magic has a tendency of leaking over, especially when a North wind blows.

The complexities of the magic system is worth noting, however. While both require will power, free magic is wild, untamed and associated with chaos and disorder while Charter magic is considered "good", requiring certain symbols to be formed in the casting.

Necromancy is considered a form of free magic, and it's tools include a sword and a set of seven bells, but the power lies in the tone, not the bells themselves. They can be used for more than just the binding of the Dead.

Ranna, the Sleeper. Has a sweet gentle tone.
Mosrael, the Waker. Wakes the Dead, at the cost of sending the ringer into Death.
Kibeth, the Walker. Allows the Dead to move, from or to Death. Can also cause wielder to go where they would not. Is rather raucous in tone.
Dyrim, the Speaker. Gives the Dead a voice, but can also silence a voice.
Belgaer, the Thinker. Returns the memories of the Dead, along with independent thought. Also can erase it.
Saraneth, the Binder. Binds the Dead to the wielder's will.
Astarael, the Sorrowful/Weeper. Banishes all who hears it into Death.

(The Abhorsen is able to use both Charter and free magic spells.)