Can I summon Interplanetarypurplythorny Dragon in response to The Monarchs Stormforth?
No, Player B cannot special summon IPPT Dragon in this scenario.


  If a monster you control is destroyed by battle or card effect and sent to the Graveyard: You can Special Summon this card from your hand.


Tributing a monster is not considered destruction, so the requirements to activate IPPT Dragon's effect have not been met. Note that any card effect is not considered to destroy anything unless it explicitly states so.