The Mist Cave is enveloped in a fog effect that was very impressive in 1991. It's a pretty simple cavern without any worrisome enemies. Kain's spears are especially effective against SandMoths, and he can Jump on SwordRats to prevent them from counterattacking.
Shortly after the first chest, which is in plain sight, head north up the short stairs to find another. Soon after, head south and around the central chasm for the third chest.
Heal up before approaching the exit, because you're about to take on the first boss of the game. The Mist D. isn't very threatening if you know what to do. Attack it normally until it turns to mist, then stop, or it will retaliate with a multi-target counterattack. Kain can still Jump when it is in mist form, and you can use this fact to get a Jump on the Mist D., but it's unlikely to make much difference. Use the time during mist form to heal the party with Potions if necessary.
Shortly after the first chest, which is in plain sight, head north up the short stairs to find another. Soon after, head south and around the central chasm for the third chest.
Heal up before approaching the exit, because you're about to take on the first boss of the game. The Mist D. isn't very threatening if you know what to do. Attack it normally until it turns to mist, then stop, or it will retaliate with a multi-target counterattack. Kain can still Jump when it is in mist form, and you can use this fact to get a Jump on the Mist D., but it's unlikely to make much difference. Use the time during mist form to heal the party with Potions if necessary.