Entangling thorns T3 immobilize cannot be dispelled or blocked and ignores unstoppable.

[Strotch]

Ivy's T3 upgrade for entangling thorns cant be dispelled by items/abilities, pierces unstoppable effects and counterspell. Only thing that stops it is Apollo riposte.

 

[alizardnamedlizzy]

Corroborating this. happened during a match (65583434) about 30-40 seconds into round 4 in Street Brawl, clip provided. In short, Doorman got rooted despite having Unstoppable during T3 Hotel Guest.