Bloodseeker's Rupture

Information on skills that deal damage by HP removal :
 From Dota2Wiki

HP Removal works by directly subtracting hitpoints from the affected unit. It ignores all damage reductions and affects units under magic immunity and does normal damage against ethereal units. HP removal will also damage through invulnerability, with the exception of Invoker's EMP. Unlike all other damage types, HP removal is not seen as damage by the game, so it will not interrupt Healing Salve or trigger any other on-damage effects such as Spiked Carapace. The following abilities count as HP removal damage:

    Won't be blocked by invulnerability and continues to deal damage (Ball Lightning, Omnislash, Time Walk, Snowball, Burrow Strike, Waveform, Refraction, Kunkka's CoCo Rum, Overcharge, Dispersion, Bristleback, Backtrack)
    Can't get reduced by magic resistence or armor
    Doesn't disable Blink Dagger
    Won't end consumables such as Clarity or Salve
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Also on Rupture:
    Can't get purged or dispelled by any living source (includes: Bloodrage, Euls, Diffusal Blade, Manta Style, Surge, Repel, BKB, Aphotic Shield, Demonic Purge, Dark Pact, Time Lapse, Kraken Shell, Infest)
    Rupture debuff will be lost upon death (includes: Aegis, Reincarnation, Super Nova or (self)denies by Bloodrage, Nightmare, Rot, Unstable Concoction's Stun, Death Coil, HotD, Life Break, Bloodstone and Suicide Squad Attack)
    Currently (might change): Deals 3 dimensional damage - affects: Toss, Euls, Ravage, Torrent etc. (going up and down both deal damage)
    Might affect Pandarem Brewmaster during Primal Split (due to the way it´s coded)

Sources reddit