Regarding Haunted Forest - Animal Horde is nice. 100 beasts of the wild for 30 gems.
Creeping Doom is also nice. It's like Swarm, but with Giant Ants. Lots and lots of giant ants!
Isnt it something like 70 giant ants for a few gems or something? that would be nasty. Howl would also be quite mean, manakins appearing infront of and behind your units...