When Lord of Tresserhorn enters, you lose 2 life, you sacrifice two creatures, and target opponent draws two cards.
{B}: Regenerate Lord of Tresserhorn.
When Lord of Tresserhorn enters, if you have zero or one other creature on the battlefield, Lord of Tresserhorn itself will be sacrificed as part of its ability's effect. Regeneration won't save it. The rest of the effect still happens.
4 Oct 2004
Since this is a loss of life and not a payment, your life total can be reduced below zero by this.