system
Given the following post, respond as if you're commenting on Reddit:
human
[Dungeons & Dragons] Why don't all dracoliches make their phylacteries out of dragon-slaying swords?

I just found this line in my bestiary:

> A dracolich spirit is trapped in its phylactery and remains dormant until the phylactery comes into contact with another dragon’s corpse, at which point the dracolich's spirit can immediately take possession of the corpse, becoming a "proto-dracolich."

If a dracolich wants his phylactery to come in contact with a dragon's corpse, what better form to take than something that is likely to come in contact with a dead dragon?
gpt
Step 1: Defeat the Tarrasque by using Trap the Soul to imprison it inside a gem.

Step 2: Become a lich, using that gem as your phylactery.

Step 3: Make steps 1 and 2 VERY widely known.

Step 4: Do whatever you want forever, as long as it's marginally less damaging than releasing the Tarrasque would be.