Cannot be Normal Summoned or Set. Must be Special Summoned by "Yubel - Terror Incarnate", and cannot be Special Summoned by other ways. This card cannot be destroyed by battle. You take no Battle Damage from battles involving this card. At the end of the Damage Step, if this face-up Attack Position card battles with an opponent's monster: Inflict damage equal to that monster's ATK to your opponent, also destroy that monster.
Destroys opponent's monster and inflicts damage to your opponent.
Destruction effect does not target.
Difficult to summon.
Does not summon any Yubel like previous forms.
Arguably weaker than previous form.
It might be dangerous to intentionally go into this monster from Yubel - Terror Incarnate as this Yubel does not have any protection or floating effects in case it leaves the field.
Yubel has 3 forms each stronger than the last and needing the previous to be summoned. The best way to special summon the original Yubel is with Limit Reverse so that you can easily destroy it by switching battle position turning it into Yubel - Terror Incarnate which needs no cost to stay on the field. Yubel - Terror Incarnate destroys every monster on the field during your End Phase. If for any reason Yubel - Terror Incarnate leaves the field you can then special summon Yubel - The Ultimate Nightmare which destroys any monster it battles and inflicts damage to your opponent equal to that monster's attack.
Give your opponent monsters for Yubel - The Ultimate Nightmare to attack into and deal damage. Lava Golem gets rid of 2 monsters your opponent controls and can be attacked by Yubel to deal 3000 damage. Destiny HERO - Departed is special summoned to your opponent's field every Standby Phase, so you can keep attacking it with Yubel to continuously deal 1000 damage every turn.
Then yes, you cannot pay because you don't have enough LP.
If you pay 1000, you'd only have 1200 LP left, and you are going to take 2000 damage from Yubel Ultimate Nightmare's effect. So you will lose the duel because you pay a cost. To prevent this, game mechanic rules that you are not allowed you to pay.