A doctor from hell.

|Devil Doctor Avatar|???|????|Fiend/Effect|Dark|5||2100|900|When a face-up monster you control is destroyed by your opponent's cards: You can Special Summon this card from your hand. You must control no Spell/Trap Cards to activate and to resolve this effect. When Special Summoned this way, activate the appropriate effect, based on the type of destruction. - Battle: Tribute the monster that destroyed that monster by battle, then Special Summon the destroyed monster but its effects are negated. -Card effect: Target 1 face-up monster your opponent controls and banish 1 monster in your opponent's Graveyard; reduce that target's ATK equal to the monster that was banished this way, then inflict damage to your opponent equal to that amount. The effects of "Devil Doctor Avatar" can only be activated once per turn.|

For battle: do you summon it to your or your opponent's side?

Good card. I would use it in a fiend deck.

It considered your side, it is your monster that you reviving.