Harvested Tension

If a permanent you control has both a +1/+1 and
a -1/-1 counter placed on it, you may remove X
+1/+1 and X -1/-1 counter from it, with both X
being equal to each other. If you do so, put X
tension counters on Harvested Tension.
{t}, remove X tension counters from Harvested
Tension: Add half {x}, rounded up, to your mana
pool.