History of Bloodsuckers

Bloodsuckers is a Gambit team medal: "As a team, drain a large portion of the opposing bank's contents in a single round." The triumph needs the medal 10 times.

How to complete

1. Bank Motes to spawn Blockers on the enemy bank. Per Destinypedia, when two Blockers exist at once the blocked team's bank takes a drain effect of one mote per second.
2. Keep two or more Blockers alive on the enemy bank as long as possible; the longer the drain, the more motes are lost. Send big deposits (for example banking 10 to 15 motes at once, since a player can hold up to 15) to spawn larger Blockers.
3. Coordinate with teammates so the enemy cannot kill the Blockers quickly. Invaders and the Primeval phase change the pace, so aim for rounds where the other team banks late.
4. Repeat until you have 10 medals. Medals are earned as a team, so a coordinated fireteam helps.

Unconfirmed

The exact mote threshold for the medal is not stated in the sources I opened. The seal and any reward were not found, so none is claimed.