How do you 'tendril feed' off someone's energy if you are not a psychic vampire?

The answer to this is the last ability learned by the psychic vampire - the ultimate stage of the vampyre condition. A description of such can be found in the story 'The Shunned House' by H.P. Lovecraft.

The means is poorly understood but one description reads

'Open all, become vacant. Reach, extends, envelop and embrace. The warm will flow the heat will come the the frost will melt...'