Baral and Kari Zev

The spell you cast from your hand without paying its mana cost is cast during the resolution of the triggered ability. Timing restrictions of that spell based on card type are ignored. It will resolve before the spell that caused the ability to trigger.

If you cast a spell without paying its mana cost, you can’t choose to cast it for any alternative costs. You can, however, pay any additional costs. If the spell has any mandatory additional costs, you must pay those.

If the spell has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

Baral and Kari Zev will count any instant or sorcery spell you cast during a turn, even if it wasn’t on the battlefield at the time. This means if you cast an instant or sorcery spell, then Baral and Kari Zev comes under your control, its triggered ability won’t trigger that turn.