New spells.

The Hive doesn't seem very effective either...

The Hive pushes back on the scale, as Ghost already mentioned, but it's worth adding that it doesn't affect undead, elementals, or mechanics. It's still worth using it when fighting against a single enemy stack so that others don't destroy the Hive, and then you won't even need other spells – the Hive will finish them all off on its own. Even if the stack contains 1000 peasants or other low-initiative creatures, as long as the enemy hero doesn't come up with anything against the Hive.

It's scary to think: an Elf with a Rain spell, cast with Crystal...

I've never done that before. I prefer to have the Elf cast Fireball, and considering that 50% of the defense is removed for 1 turn on affected stacks, it turns out to be very effective.