Once Unholy Indenture returns the creature, it’s considered a new object with no relation to the object that it was. Auras that were attached to it won’t return to the battlefield (including Unholy Indenture itself). Equipment that was attached to it will remain unattached. Any counters that were on it won’t be put on the new creature.

You control the returned creature, regardless of who controlled it before it died.

If the returned creature enters with any other counters, it enters with those counters plus an additional +1/+1 counter.

If Unholy Indenture enchants a token, it won’t be returned to the battlefield when it dies.

If multiple players each control an Unholy Indenture attached to one creature, the player who will control the returned creature is the last player in turn order from the player whose turn it is at the time the creature dies. In a two-player game, this means the player whose turn it is not. In a multiplayer game, this means the player closest to the right of the player whose turn it is.

In a multiplayer game, if a player leaves the game, all cards that player owns leave as well. If you leave the game, the creature you control from Unholy Indenture’s effect is exiled.