A solid and reliable demon for a slow team on Aura gate, specially at 40+ levels. No Weakness means no turns lost to vulnerabilities. Gluttony works well on several annoying encounters, hits hard, and gives him health. You can get him purple, for Makara Shift, on Aura gate. For other uses, Yellow's Sea of Chaos is pretty neat.
Conventional wisdom says Yellow with Divine Brands for quick Gluttony/Mazionga/ Sea of Chaos. +Mag atk% primary
Purple can get Divine, Spell or Life brands, with + Mag atk % primary, and if you can + Heal % secondaries. And works well with Intimidating Stance teams.
Many people like Yellow Beelzebub for Sea of Chaos, but he is somewhat outclassed by King Frost, who has comparable Magic, a +15 % Ice damage, and Cold World has a higher 130 power, at just 7 mp. Ice NDR demons are somewhat uncommon in the meta, and even if a Demon got Resistance to Ice he should still take more damage from Cold World than he would from Sea of Chaos.
The relevance of this statement is that on a meta full of Physical Pierce demons, both Beelzebub and King Frost get in their clear version the buffed Wild Instinct, that reduces by 75% the critical hit rate of enemies. That means taking less damage, and more importantly, a well built team can greatly reduce the enemy's press turns.
Adding Dark Pierce to Beelzebub may enhance his gluttony further, allowing to bypass Masakado and other NDR Demons and give him great staying power. But if Beelzebub is the last demon acting, it may be entirely unnecessary.