In your chatbox, you will notice 'Olm lets out a cry...'.
He will target a single player with a red glowing aura.
Crystals will fall from above on this player continously
for a few moments. Damage will be dealt to those in
the targeted tile of the crystals as well.
To dodge these crystals, you can simply turn off your
run and walk around the olm room. Preferably away
from any other players. If you become electrocuted
in the process, you will be bound and crystals will
rapidly fall on you.
Olm will shoot out 1-2 crystal bomb(s), sometimes
up to three in larger groups. The bomb will explode after
being live for a few moments. It's range is 5x5 and the
minimum damage you can deal from it is 15. The closer
you are when the bomb goes off, the more damage is inflicted.
In order to avoid these bombs, simply run
as far away as you can from them.