If this card is sent from the field to the GY: Add 1 monster with 1500 or less ATK from your Deck to your hand, but you cannot activate cards, or the effects of cards, with that name for the rest of this turn. You can only use this effect of "Sangan" once per turn.
Searches your deck for a wide variety of monsters.
Effect activate when sent from field to the graveyard not only when destroyed.
Needs to be sent from the field to activate effect.
You can set Sangan and let your opponent destroy him so that during your turn you can use the effect of the monster you searched.
Sangan's effect also activates when you use him as tribute for a tribute summon, or ritual summon. But for ritual summon keep in mind he must be on the field first to activate his effect.
Sangan's only search restriction is attack points. You can search out a monster with as much Defense, level, and whatever type and attribute you want as long as it falls with the 1500 or lower attack restriction.
Send to the Graveyard
You can use these cards to send Sangan to the graveyard during your opponent's turn so that you can activate the effect of the monster you searched.
Are you sure it's not treated as zero? When experimenting in friend duels I put Cat Sith in defence mode. My friend had Ra on the field he attacked and Ra's attack was reduced to 200. When the turn was over Ra's attack was zero.