Ornns ult cant be recast when low on mana.
just tested it in the practise tool. when casting the ult takes you below 100 mana, youre unable to reactivate it to redirect the ram.
and here i sit and wonder why i sometimes couldnt recast the ult in teamfights despite not being cced.
since only the initial cast of the ult is supposed to cost mana, and not the reactivation, the fact that the ult recast is disabled below 100 mana seems like a bug to me.
edit.: ok, thats weird. i just tried another time and this time it worked. nvm i guess?