One is Stardust Dragon/Assault Mode:
This card cannot be Normal Summoned or Set. This card cannot be Special Summoned except with its own effect or with "Assault Mode Activate". You can Tribute this card to negate the activation of a Spell Card, Trap Card, or Effect Monster's effect, and destroy that card. If you negate an effect this way, you can Special Summon this card from your Graveyard during the End Phase. When this card on the field is destroyed, you can Special Summon 1 "Stardust Dragon" from your Graveyard.
Stardust Assault has a Summoning Condition that restricts every possible method to Summon it, other than Assault Mode Activate or its Trigger Effect. Speaking of which, Stardust/Assault is very similar to Stardust Dragon: It has an Optional Quick effect that negates other effects, and an Optional Trigger Effect to Summon itself. Every rule on Stardust also works for Stardust/Assault Mode: The negation effect can be activated during the Damage Step, the tribute is a cost, and so on. In addition, much like the other Assault Mode monsters, Stardust/Assault has an Optional Trigger Effect that Summons its previous form. This effect targets, and will activate even if Stardust/Assault is destroyed and Removed from Play (such as with Bottomless Trap Hole). Note that the target must have been properly Synchro Summoned, so if you used Starlight Road, you cannot Special Summon a Synchro Stardust Dragon with this effect.
The other dusty dragon is the upcoming JUMP Promo, Malefic Stardust Dragon:
This card cannot be Normal Summoned or Set. This card cannot be Special Summoned except by removing from play 1 "Stardust Dragon" from your Extra Deck. There can only be 1 face-up "Malefic" monster on the field. Field Spell Cards cannot be destroyed by card effects. Other monsters you control cannot attack. If there is no face-up Field Spell Card on the field, destroy this card.
Malefic Stardust has the staple abilities and restrictions of Malefic monsters: A Summoning Condition that prevents its Summon except by Removing from Play the original monster, a Condition that allows you to control only one Malefic monster, a Continuous Effect that restricts your other monsters from attacking, and a Continuous Effect to explode if you don't have a Field Spell Card. Other than that, Malefic Stardust Dragon has a Continuous Effect that prevents Field Spell Cards from being destroyed by Card Effects. Note that activating a new Field Spell Card is not a Card Effect, so they can still be destroyed by this method.
So yeah, a very short article T_T If you have any questions, feel free to drop me an e-mail at ness00[at]gmail[dot]com.