Siphon Life (rank 2)

• Demon SkinLevel 1 · Rank 1
• Shadow BoltLevel 1 · Rank 1
• CorruptionLevel 4 · Rank 1
• Curse of WeaknessLevel 4 · Rank 1
• Life TapLevel 6 · Rank 1
• Bane of AgonyLevel 8 · Rank 1
• FearLevel 8 · Rank 1
• Create HealthstoneLevel 10 · Rank 1
• Drain SoulLevel 10 · Rank 1
• Health FunnelLevel 12 · Rank 1
• Curse of RecklessnessLevel 14 · Rank 1
• Drain LifeLevel 14 · Rank 1
• Create SoulstoneLevel 18 · Rank 1
• Demon ArmorLevel 20 · Rank 1
• ShadowburnLevel 20 · Rank 1
• Drain ManaLevel 24 · Rank 1
• Curse of TonguesLevel 26 · Rank 1
• BanishLevel 28 · Rank 1
• Siphon LifeLevel 30 · Rank 1
• Subjugate DemonLevel 30 · Rank 1
• Shadow WardLevel 32 · Rank 1
• Create SpellstoneLevel 36 · Rank 1
• Curse of IdiocyLevel 38 · Rank 1
• Howl of TerrorLevel 40 · Rank 1
• Death CoilLevel 42 · Rank 1
• Bane of DoomLevel 60 · Rank 1
• Curse of AgonyRank 7
• Curse of DoomRank 2
• Curse of the ElementsRank 1
• Dark PactRank 1
• Fel ArmorRank 1
• Ritual of SoulsRank 1
• Seed of CorruptionRank 1
• ShadowfuryRank 1
• Unstable AfflictionRank 1

The free addon pack puts it on your bars, or see the whole Warlock spell list.