So I had the match basically won with a bunch of heavy hitting effects on the board.
- Ral, Izzet Viceroy's emblem allowing me to do 4 damage to any target and draw 2 cards whenever I cast an instant or sorcery
- Jaya Ballard's emblem allowing me to cast instants/sorceries from the graveyard
- Thousand Year Storm allowing me to copy each instant/sorcery for each time I cast a previous instant/sorcery
- ...and a whole bunch of instants/sorceries and the mana to cast them.
I wanted to use the instant "Shock" last (deal 2 damage) to make maximum use of Thousand Year Storm's effect but since I had removed all my opponent's non-land permanents from the board, I used some draw spells to build up TYS and trigger Ral's emblem, and after my library was fully drawn I finally cast shock to take my opponent down to -2 life. That should have given me victory, except...
I was of the understanding that I'd only lose on drawing out my library at the beginning of my next draw step... but I misunderstood the ruling, apparently I lose upon being forced to draw from an empty library at any time (I had to draw due to Ral's emblem).
... so because I tried to draw from an empty library at the same moment my opponent went to -2, the game decided to end the match in a draw.
-_-
Magic the Gathering Arena