7. Keywords and effects
Tank
A unit that has to be dealt with first
In a combat, you choose how your damage is split, as long as each unit gets lethal damage before the next gets any. A unit with takes some of that choice away: it has to get its lethal damage before any of its friends without Tank get theirs.

An example
Your opponent defends a battlefield with (2 , Tank) and a (3 ). You attack with a , which deals 4.
- Without Tank, you'd put 3 on the Skulker and kill it, and the last 1 on the Yordle.
- With Tank, the Yordle comes first. 2 of your 4 kill it, and the 2 left aren't enough for the Skulker. It lives.
So Tank protects whatever's behind it, as long as it's still standing. It doesn't make the unit itself any tougher.
More than one
If your opponent has two units with Tank in the same combat, you choose which to deal with first, but both need lethal damage before anything else gets any. Tank only matters to the side dealing the damage: your own Tank doesn't change how you split yours.
Try it
Attack into a unit with Tank, and see where your damage has to go.