We're just starting a campaign, and a player wants to create a very distinct character... a Pelor's Blackguard. Yes, a PELOR Blackguard. Is that possible to create Blackguard that follows Pelor in 4e? If it is possible could you explain me how?
Simple: he is a true believer of the true Pelor, The Burning Hate.
It’s just fanon, but it’s a pretty fun one. Might make for a really cool character, and a very interesting plot hook. Depends whether or not you had important plans that hinged on Pelor being as described in the books.
In 4e divine power doesn't come with all the alignment constraints it had in prior editions; gods rarely involve themselves in the mortal plane, especially to empower/disempower individuals. If a follower of a god turns against their tenets (such as a servant of Pelor becoming unaligned or even evil), the god won't (can't?) just cut off the character's power. The god may send other mortal servants after the wayward character, but the character's power won't simply disappear.
Also, it's possible that the character may worship Pelor but not actually like Pelor or believe in his tenets. Perhaps he was saved by a priest of Pelor once and feels obligated? Maybe he believes it will shield him from a curse? Or he wants/needs the aid of Pelor's church for something? Perhaps his faith is sincere but he's been mislead about what Pelor stands for and how Pelor wants his servants to act?
Or maybe he's just a jerk.
Its valid to point out that depending upon the chosen vice Character Builder/RAW locks you into alignments between chaotic evil to unaligned or chaotic evil to good. I think this is inherently silly though as no other classes (or anything else for that matter) have any real restrictions similar to this and beyond that the alignment system is pure fluff in 4e anyway. A Lawful good Blackguard would basically be a Paladin fueled by his hatred of evil/his god's enemies (like the fluff for the Avenger class) rather than upholding/promoting their tenets and being an all around hero. Silly example: Batman is a blackguard, Superman is a paladin. TLDR; Just house-rule the alignment out.
I believe you'd have to define what you mean by 'Blackguard'. Are you referring to the Class, or simply the position it sounds like?
You could go with the 'Necessary Evil' path. Being 'Good' doesn't count for anything in terms of achieving victory against 'Evil', Sometimes 'Bad' things must be done in order for 'Good' to triumph.
It could also be that Pelor do have Blackguards, they just aren't Public (or perhaps even official) -a small elite squad- that works for Pelor, perhaps they are even the ones that deal with Pelor's followers when they step out of line.
I (personally) wasn't satisfied with DnD's Pantheon, so I created one based on my own views -using names and the general style of DnD to keep it familiar to the players-. In my universe I define Pelors influence from his Divinity 'Sun', which reperesent Time, Light and Fire, which essentially makes him a God of Time, Light and Fire, but because Light collides with 'something' a 'Shadow' is created -Shadows are born from Light- therefor Pelor is also a God of Shadow (his influence over that domain is as Absolute as a Shadows relation to Light, but he only hold indirect control/influence), but in the end all Shadow's are bound to the Light, and therefor serve the Light. Based on this Style you could have a Blackguard serving Pelor.
(P.S: if you want I can tell you what Lolth think of Pelor's influence over her and her domain ^^).