Wouldn't the "add this card from your deck to your hand" part of the effect have to be activated by the monster?
On second thoughts, Dark Sage also states that he can be searched from the deck.
I've always thought it was kind of weird that a card's own effect searches itself from within the deck.
Also, wouldn't it's effect mean that it would be free discard fodder? Kind of like the banned card Sinister Serpent?
If that was the case it would instantly break Brionac.
You could change the text to "When sent to the grave after activation" for clarification.
It would be a very powerful card(most likely banned), seeing as you can use it all three times in one turn to clear the field and decimate your opponent. this is made easier due to it being a "half your own lifepoints" spell. So it is unable to actually kill you.
Although, in one turn you could potentially drop to 1000 lifepoints.
This can be evaded by smart choices of cards.
I'm sure there is a spell card which adds together both players' life points and divides them equally. This would serve to burn the crap out of your opponent, putting them at 4500 after one turn (easy OTK range) and basically removing the cost for your spell abuse. and that is only during the first turn.
Imagine if you both had 3000 life points left.
You use that card to clear then divide the lifepoints.
1518 lifepoints each and you have a clear field.
madness I tell you.
If it existed and was at 3, everyone would run 3 of them and three Winged Kuribohs.