Permanent arrays became much less effective if their owner was away for an extended period of time. Their imprint would start to fade and without the owner's instructions, a skilled intruder could bide their time studying the arrays and take them down one at a time.
The solution to this problem was to share the control over the arrays like the nobles did in the Kingdom, pass it to a trusted individual like Scarlett had done to Kalla back when she left to chase after Balkor, or a signet ring.
Red mana crystals could accept more than one energy signature but their charge would only last for so long. The signet ring meant that Barham didn't trust his apprentices not to shut down the arrays and kill him if he shared control or give him control over his mansion back once he returned.
Lith knew that a signet ring was a Forgemaster's last resort and so did Strider.
