Omni bestow

[blabla]

ok, so say i have an  {Omniscience} In play.
Can i bestow for free? Or is the bestow already an alternate cost? Not sure if it's a mode or a casting cost. Thanks.
(Bestow from my hand btw)

[Remillo]

You still have to pay the cost.  When you cast something "Without paying its mana cost", it creates an alternative cost for casting that spell.  Now, you can only ever pay ONE alternative cost when casting spells, so you'll always have to choose one.  Things like Bestow and Overload are also alternative costs, so you can't cast them for free using Omniscience.  You can't cast your Chromanticore or Overload your Cyclonic Rift for free.

[Dsx Cherno]

Also, any spells with {X} you cast for free automatically cast as {X}=0