"The Dark - Hex-Sealed Fusion" can be used to Summon this card, reducing the number of cards required to Summon this card from 3 to 2.
With the release of "Archfiend Black Skull Dragon", this card has been largely outclassed. Not only does "Archfiend Black Skull Dragon" have less specific Fusion Materials, but it also has several useful monster effects with no major drawbacks. With this in mind, "Black Skull" does offer several useful functions "Archfiend Black Skull Dragon" cannot.
Since this monster lists specific Fusion Materials, "Elemental HERO Prisma" can be used to send either "Summoned Skull" or "Red-Eyes Black Dragon" to the Graveyard with its effect. If there is the other Fusion Material in your Graveyard, "Dragon's Mirror" can be used to easily Summon this card (or "Archfiend Black Skull Dragon").
With these two tips in mind, it is worth it for any "Red-Eyes" Deck to include at least 1 "Black Skull Dragon" to fuel these support cards– even if it is never actually Summoned.
This card can gain also immunity to Spell Cards with "Non-Spellcasting Area", given that it is a non-effect Fusion Monster.
In addition, "Daigusto Emeral" can be used to repeatedly revive this card.