Complex sentence: Only those of the Belmont bloodline are able to use the whip's full potential without paying a price, for the whip simply drains the life of users who are not of the Belmont lineage.
Split into simpler sentences: Only those of the Belmont bloodline are able to use the whip's full potential without the cost of one's life. The whip simply drains the life of users who are not of the Belmont lineage.