Epic Encounters: Chambers of the Serpent Folk (D&D 5E Compatible) 017 you may put Nether Shadow

you may put Nether Shadow onto the battlefield

elementals

Whenever Balefire Dragon deals combat damage to a player

Or if you were facing a Zombie-Dinosaur player instead and he created an epidemic of massive beasts at the same time

Epic Encounters: Chambers of the Serpent Folk (D&D 5E Compatible) 017 you may put Nether ShadowIn the deep past of the world, the serpent folk rules over all. For millennia they have waited, preserved in the hidden places of the Earth. Now, their forgotten temple is beginning to echo with the sibilant hiss of strange poetry, and the screech of sarcophagus lids shoved aside as scaled hands emerge. Now, they are awake. And they are wanting. Inside this box is everything you need to run a truly epic encounter. Perfect for new and experienced