Tecutlan, the Searing Rift
Flip Brass's Tunnel-Grinder into Tecutlan, the searing rift, then if you have forgotten monument in play and try using it to tap Tecutlan, the searing rift by paying 1 to get any color mana it causes the match to end as a draw.

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ASGREVE#61644 commented
the same happened to me today, had tecutlan and chromatic lantern in play. i tried to understand wtf happened in the match and tried to reproduce the bug against sparky, and i noticed that whenever i tried adding mana of any color other than red, the match ended as a draw. that didn't happened when i added red mana.
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Jigstack#88178 commented
Bug still not receiving traction, what a joke of a reporting system.
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Tap Tecutlan, the Searing Rift (transformed Brass's Tunnel-Grinder) to add one mana of any color using Forgotten Monument's ability and the game ends in a draw.
This happened twice in two different games. I tried to upload my logs, but it keeps timing out. Please refund entry fee. -
Jigstack#88178 commented
Tecutlan, the searing rift (flipped Brass's tunnel grinder