Beseech the Mirror Chronicles damage that would reduce your

damage that would reduce your life total to less than 1 reduces it to 1 instead

you may put a +1/+1 counter on Thraximundar

reference booklets

Whenever an opponent casts a creature spell

it deals that much damage plus an amount of damage equal to the number of fire counters on this enchantment instead

Beseech the Mirror Chronicles damage that would reduce yourBargain (You may sacrifice an artifact, enchantment, or token as you cast this spell.) Search your library for a card, exile it face down, then shuffle. If this spell was bargained, you may cast the exiled card without paying its mana cost if that spell's mana value is 4 or less. Put the exiled card into your hand if it wasn't cast this way.