Orchid facts

Bought From:
Arcane Sanctum

A garnet rod constructed from the essence of a fire demon, Orchid Malevolence can burn away an enemy's spellcasting capabilities for a limited time.

+20 Intelligence
+30 attack speed
+45 damage
+225% mana regeneration
Soul Burn (active)

3 X Oblivion Staff (1675)

Soul Burn
Silences a target unit and amplifies the damage it takes by 20%
Amplified damage is dealt at the end of the duration as magical damage
Lasts 5 seconds, costs 100 mana, has a 18 second cooldown, and a 900 cast range

Silence BLOCKS these passives:
1) Last Word Aura
2) Permanent Invisibility (Riki's and Mirana's ultimates!)

For more info:
Official Item Page
In-Depth Thread