Obelisk is quite powerful on his own right. A 4000 ATK & DEF beater that can't be targeted by Spells, Traps & Monster Effects and whose Normal Summon can't be negated.
Plus, he can clear the opponent field of monsters if you tribute other 2 monsters you control (even when he can't attack if this effect is used, that's a powerful effect).
No wonder why he is not released yet...