Twilight III help
It’s tricky because typically Tequatl never recovers from being stunned by the laser before the each defence phase starts, but it is still possible (it took me about three weeks of trying daily).
As soon as Tequatl’s health reaches 75% and the first defence phase starts, a vortex will spawn. I found that standing in melee range of Tequatl’s left foot, and slightly to the side was a good spot. Look out for a pair of the bone fingers that appear and swirl round for a second or two – that is the vortex appearing. If you see that, run to where they are (make sure you do not dodge) and hopefully you’ll get pulled in.
If you get lucky and get a map with population low enough not to damage Tequatl too quickly, but high enough to get to the first defence phase, you may also see vortexes appear after Tequatl recovers from being stunned by the laser, but it’s really hard to get such a map.