Mystral vs. Vecna

In the campaign im participating in, my character is a wizard/warlock with Vecna as his Patron, his ultimate goal being to achieve lichdom. In order to obtain more knowledge about magic in general to continue his research, im considering taking a dip in arcana cleric of Mystra to get some divine help and those sweet, sweet, cleric spells. The problem is that Vecna is NE and Mystra is NG, so I really don’t know how they would get along. I know that they are from different worlds and that the Greyhawk version of Mystra taught Vecna all he knows, but I don’t know if their differences in opinions would make it difficult for my character, or if Mystra likes liches-to-be for that matter. personally, I would like to be able to work cooperatively with Laeral Silverhand instead of trying to kill her. Again.