The IRS

At beginning of upkeep, player chooses opponent
to tap a land or artifact that gives mana. Tapped land becomes unusable until that The IRS's next turn and mana is cumulatively stored with a +1 counter for every time this is done.

{t}, The IRS uses the mana built up and +1 counters reset

I Don't Care Who the IRS Sends, I Am Not Paying Taxes