Here is the list of enemies your likely to encounter when you are playing.

Enemies	Spell Needed	Description
Gnome	Flipendo	From the first game, these are pesky little creatures that love beans. All you need to do is use flipendo to stun them. Yet in this game, there is always a small cave near a gnome, in which you can throw them in to get more beans.
Firecrab	Rictusempra	Firecrabs come in two sizes. The smaller ones need one good hit of rictusempra to stun them for a while. The larger ones need to be hit 2 times to get stunned. Their main weapon is that they shoot fireballs from their behind. It can get quite hectic when there are more than one. For this, the best thing to do is to stun them all first, and then do what you wish.
Snails	Rictusempra	Another enemy from the first game, yet these ones are a bit more aggressive. If you are near, they will come at you with full speed.
Cornish Pixies	Rictusempra	These are pesky little creatures that can be found anywhere. One good spell can get them easily. If they come near you, they will attack
Tiny Spiders	none	These little things are also all over Hogwarts. They are really annoying because they will get on you if you stand still for even a moment. The best thing is to just step on them.
Large Spiders	Rictusempra	These are a lot larger than the small ones and require a spell. Yet the good thing about these is that once you stun it, it will stay like that.
Bowtuckles	Rictusempra	Another bunch of annoying creatures. Usually found around wiggentrees, they throw bark at you if you are near. When you hit them with a spell, they leave behind a wiggentree bark for you to use in your potion.
Spiky Bushes	Diffindo	These plants have several thorns that it shoots out if you come to close. One spell will make them go away.
Venemous Tentacula	Diffindo	Another plant found around Hogwarts, especially the Greenhouse. This plant usually has 2 or more tentacles, and one mouth in the center. Hit all the tentacles to stun it completely.
Horklump Mushrooms	Diffindo	These mushrooms spray a poisonous gas if you approach it. Cut them with diffindo, or if there is a gnome nearby, let it eat them. If you cut the mushrooms, you can use them as weapons.
Imps	Rictusempra	These are almost the same as gnomes, yet alot meaner. As soon as they see you, they will run at you, and are very quick. Like with the gnome, stun them and through them into little holes. There are usually more than one around in some areas.
Ectoplasm	Skurge	These are greenish substances left behind by ghosts. If you touch them, you will start losing your stamina. They are usually found in dark places, like the dungeon.
Peeves	Skurge	Again, you must face Peeves. He is the school's poltergeist. Once, you will have to face him, and then he will sometimes hide in chests around the levels, so be careful/
Aragog	Rictusempra	One of the main bosses you will find here. From what I've read, the way to beat it is to stop and let it rise so that you can hit it's belly with your spell. Yet I have been able to defeat it without getting a scratch. You need to use your mouse for this. Just keep running and hitting Aragog with your spell, and DO NOT STOP. It will take some time, but if you notice, his health will decrease slowly. This way, you dont get hurt as well and you defeat him.
Basilisk	Rictusempra	The main boss of the game. All you need to do is shoot your spell when its mouth opens. For me, I was only able to aim right if i was very close to him. So to each their own :)