Does the "any amount of your damage is enough to kill" mean any damage from any source?

Yes, Elder Dragon's ability applies to any damage you deal to enemy units, regardless of the source, as long as you are the one controlling that source.

According to RiftJudge FAQ #8684, Elder Dragon's ability modifies how your damage interacts with enemy units. It does not matter if the damage comes from a spell, an ability, or combat; if the damage is yours and it is dealt to an enemy unit, that unit is killed.

Key points to remember:

• "Your damage": You must control the source of the damage (e.g., a spell you played, an ability of a unit you control, or combat damage from your units).
• "Enemy units": The ability only affects enemy units. It does not protect your own units from your own damage (as clarified in FAQ #8684).
• Damage must be dealt: The damage must actually be dealt to the unit. If the damage is prevented (e.g., by Unyielding Spirit), the condition for Elder Dragon's ability is not met, and the unit will not be killed (as clarified in RiftJudge FAQ #9396).