Lux ult splits into two (no screenshot)

I had a 38 minute game on the 14th of June, I was Nautilus support laning against a Lux support (can't really remember the adc's) and my team and i all noticed that Lux's ult was splitting into 2. I couldnt tell you if both of the beams did damage, but we were all seeing it happen. she had a hextech prototype belt or something of the sorts so maybe that was it, along with her support item? not really certain but i kinda felt like it was a bug or someone was cheating but i have no idea how one would go about doing that, sorry for the paragraph, and thank you -Zukishikimirimo