Random Void Gems being created?

aenigmaeffect

I'm playing Saheeli's challenge, round 4. When the AI attacked (it had Lightning runner, Kari Zev, and Aethertide Whale), the board created a bunch of void gems. It also had a Dynavolt Tower. I had a Bloodbond Vampire.

Anyone else had something like this happen?

(This happened to another time, but not with energize creatures, on another event, and I don't know why).