Age Of Strife

Age Of Strife enters the battlefield with X
tension counters, where X is the number of
players. When the last tension counter is
removed from it, sacrifice it.
{4}: Remove a tension counter from Age Of Strife.
Any player may activate this ability.
Each attacking creature has +1/+0 for each
creature blocking it. When it deals combat
damage to a player, its controller untaps it.