Flying, lifelink
Whenever you draw a card, Dream Trawler gets +1/+0 until end of turn.
Whenever Dream Trawler attacks, draw a card.
Discard a card: Dream Trawler gains hexproof until end of turn. Tap it.
Dream Trawler’s second triggered ability resolves before blockers are declared. This normally causes its first triggered ability to trigger, which also resolves before blockers are declared.
You can activate Dream Trawler’s last ability even if it’s already tapped. It still gains hexproof until end of turn.