This might be common knowledge but I wasn't able to find anything concrete, so I figured I'd ask here.
I know Zephrys is hard-coded to give you lethal if it exists. I was playing against someone earlier who had a secret I was 99% sure was Ice Block and I had lethal in play if not for that. I drew Zephrys and thought "Sweet, I guess I'll get Flare or new SI7 dude to destroy the secret", and instead he offered Fireball, Windfury and some other nonsense.
Is there a way to have Zephrys offer you a secret-destroying card guaranteed or is it RNG?
make sure you only have 2 mana so it gives you flare
This is important to remember. Zephrys also seeks to utilize remaining mana (Zeph clearly watched Trump's old videos). If you're searching for a particular answer (like savage roar or shadow word: death) make sure to bring your mana to the right amount in order to maximize the probability that he'll offer it.
Because it is wild and you probably had lethal with not one minion but two, so he thought that vaporize would not have been a problem and gave you another way to lethal. What is strange tho that I had and Arcane tyrant and opponent exactly at 16 hp and zeph didn’t give me windfury. That was weird