If you control Bloodthirsty Conqueror and Sanguine Bond, an opponent losing life (for example from damage) will trigger Bloodthirsty Conqueror to make you gain that much life, which in turn triggers Sanguine Bond to make a target opponent lose that much life; that loss then triggers Bloodthirsty Conqueror again, and the two triggered abilities can keep creating each other repeatedly until something stops them (life totals reach 0, a replacement/prevention effect intervenes, targets are illegal, etc.). This interaction relies on the damage→loss of life rule , life-gain/loss bookkeeping and the way the life-gain trigger is treated .
Step 1
An opponent loses life (for example, they are dealt damage); damage to a player causes that player to lose life and loss of life is applied to their life total .
Step 2
That loss of life triggers Bloodthirsty Conqueror's ability ("Whenever an opponent loses life, you gain that much life"). The ability goes on the stack and later resolves, causing you to gain that much life .
Step 3
You gaining life is a life-gain event and therefore triggers Sanguine Bond's ability ("Whenever you gain life, target opponent loses that much life"); Sanguine Bond's trigger goes on the stack .
Step 4
When Sanguine Bond's triggered ability resolves it causes the chosen opponent to lose that much life; that loss is applied immediately to their life total .
Step 5
That new loss of life is another event that triggers Bloodthirsty Conqueror again, putting another gain-life trigger on the stack, and the cycle repeats.
Step 6
This creates a repeating series of triggered abilities (Conqueror → Sanguine Bond → Conqueror → ...). The loop continues until something intervenes (replacement/prevention effects, illegal targets, a player’s life reaching 0 so they lose, or other game-ending/intervening effects).
Resolution
When an opponent loses life, that loss causes Bloodthirsty Conqueror's triggered ability to trigger and (when it resolves) you gain that much life; that life gain causes Sanguine Bond's triggered ability to trigger and (when it resolves) target opponent loses that much life, which then causes Bloodthirsty Conqueror to trigger again. This alternation of triggers can repeat indefinitely, draining life each cycle, unless interrupted by replacement effects, illegal targets, or a player losing the game due to their life total reaching 0 or otherwise. The interaction depends on damage causing loss of life and life-gain/loss being applied as described in and the life-gain trigger wording rules in . Rulings note that damage counts as loss of life for these purposes [Ruling 2024-11-08] and that Sanguine Bond triggers once per life-gain event [Ruling 2009-10-01].
