I keep waiting for Redcloak to command Xykon. As a lich, # of hd isn't a strong point.
Well, since Xykon is an Epic-level Sorcerer that can cast a number of above 9th level slots, including at least 12th level Spell Slots (Maximized Energy Drain, plus Still Meteor Swarm) and the Epic spell Superb Dispelling (Spellcraft DC 59!), he's going to be at least 24th level at a bare minium (Epic Spellcasting and Improved Spell Capacity x3, that's 4 epic feats, so his 21st and 24th level feats, plus his Epic Sorcerer bonus feats at 23rd level), and probably at least 26th level for Epic Skill Focus (Spellcraft) as an Epic Sorcerer Bonus Feat at that level to get close to being able to cast Superb Dispelling, not to mention that Liches have Turn Resistance 4, so he's effectively 28 to 30 HD for turning purposes.
In terms of being able to cast Superb Dispelling, if he's 26th level then he could have 29 ranks in Spellcraft, +2 from Skill Focus, +10 from Epic Skill Focus, +2 from Magical Aptitude, and +2 Synergy (for 5+ ranks in Knowledge (Arcana) for +45 easily. If he's 27th level then he could have taken Epic Skill Focus (Spellcraft) again and have a +56 and be able to make that spell on a roll of 3 (or a 1 if he has another +2 bonus from somewhere, I have trouble believing it is from Int though).
Redcloak, we don't know how powerful he is, but the highest spell we've seen him cast is Extended Summon Monster VII (8th level), so he's probably a 15th or 16th level cleric. If he's higher level, we have no direct evidence of it.
So, we have no evidence that Redcloak could even theoretically Rebuke/Command Xykon