Easiest magic trick is summon spirt. Press Back, Forward, Up, Down then attack to cast. Just do that to 10 enemies in a row and it will unlock. I found on the outer wall with the Medusa heads was a good pace to cast the spell and dodge as opposed to using the zombies at the beginning, but either will get you the achievement.
Here is the full list of spells pulled from a FAQ by Zach Keene found on Gamespot.com:
U = Up D = Down F = Forward B = Back
Charge (button) = Hold (button) for two seconds, then do whatever.
1) Dark Metamorphosis: B, UB, U, UF, F + Attack
Whenever Alucard attacks an enemy that bleeds and touches the blood,
Alucard heals some HP. (10 MP)
2) Hellfire: U, D, DF, F + Attack
Just like Dracula. After you teleport out, press left or right to
determine where you teleport in. Then, you'll do Dracula's 3-Fireball
attack. Or, hold U as you teleport in to do Dracula's large fireball
attack. Hold D to cancel the fireball period and just have a teleport.
3) Summon Spirit: B, F, U, D + Attack
Summons spirit which homes in on one enemy. (5 MP)
4) Tetra Spirit: Charge U, UF, F, DF, D + Attack
Like above, but summons four spirits at once. (20 MP)
5) Soul Steal: B, F, DF, D, BF, B, F + Attack
Steals life from enemies and Candles. (50 MP)
6) Wolf Charge: D, DF, F + Attack
Swift charge attack. (Must be in wolf form. Requires Skill of Wolf and
Soul of Wolf Relics. 10 MP)
7) Wing Smash: Hold X (U, UB, B, DB, D, DF, F) Release X
Swift charging attack. (Must be in Bat form. Requires Soul of Bat
Relic. 8 MP)
8) Sword Brothers: D, DF, F, UF, Charge U, D + Attack
Sword Familiar does an attack which damages all on screen enemies.
(Requires Sword Card relic. Sword Familiar must be active as a Familiar.