Sure we got small bits of info and lore like from outbreak perfected, but after Rise of Iron it feels like SIVA was just completely forgotten and never mentioned in depth again. I’ve heard people call RoI a filler dlc because it was just kinda brushed under the rug and Aksis as well as the entire storyline of SIVA was just never used/mentioned again. It’s a real shame considering how unique SIVA was as well as the potential it had for further story usage.
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Long story short, SIVA was never intended to be a major thing in the destiny universe. Bungie doesn't want to use or revive it as a story last they told us (which could change) and was really a "purpose built" antagonist for rise of iron