Bug
Found a bug where using Tasha unholy archmage's +1 ability does not resolve properly and carries over into following turns, allowing for the +1 to become a lingering effect until the opponent triggers the now ridiculous stack by attacking.
Step 1: clear creatures off of field
Step 2: play Tasha unholy archmage and use her +1
Step 3: remove any creature your opponent plays on the following turn before they can attack.
If done properly, the icon representative of Tasha previous use will retain past upkeep and will begin to stack until you your opponent to attack, in which case their will instantly die due to the -1-1 counters.
I am using an android, but I have no doubt this is in more then just my os.