Serperior, some variants of the deck use one that leans more towards Gravekeeper's (like Descendant, Spy, stuff like that) and has the Malefics as an aside.
Overall it looks solid, since you want to protect your Malefics once they get out. Though, if you wanted to go for another option for a Field Spell card, you could try Geartown if you wanted, since it gets you a free 3000 ATK beater (Gadjiltron Dragon) when destroyed. It looks good, but if I had to offer any other advice, I'd put in some more lv. 4s that can do stuff for you (Descendant is good for that since it pops cards).