I really like the mystery/potential lore behind sirens, and I’ve been thinking: you remember how Tannis says there’s some connection between sirens, eridium and the vault, since Lilith got boosted by eridium, right? And people wondered why Maya doesn’t go all super saiyan too (at least not according to the lore - technically she does start throwing balls of slag after levelling up some on Pandora).
But what if Tannis is wrong? What if it’s ONLY Lilith who gets eridium powers? Maybe every siren is assigned a vault/planet, which comes equipped with a custom substance that augments their powers, and Maya just hasn’t found hers yet.
I still don’t know why a siren would get a vault, possibly they’re also defenders like the Guardians (albeit very elite, powerful ones), but unlike Guardians, they can assimilate into whatever race exists at the time, since siren powers are apparently passed on somehow? Maybe they get the extra powers in case of emergencies, like the vault opening?
Anyway, just my musings and stuff