How rare is Target spell?

[Infiltrator]

I found Res in verona and Phantom on Rusty. No Target yet

[Metathron]

I found the spell only on Tekron. However, my spell book is chock full of other (mostly useless) scrolls that I cannot buy it, and I ditched the cyclops meat tank some time ago anyway, so it wouldn't be too useful for me anyway.

[Saridu]

Dig away! Your dragon has an amazing nose for spells.

Apart from the great money and runes, I have found several mid level spells this way (Multiple copies of target and slow btw) So use treasure hunter at least twice a combat