Riddikulus!

Er, do you mean a Howler?

Ridikkulus! The Howler starts singing in a pretty nice voice.
Pop! The boggart becomes a giant slug.

viva la vida

Riddikulus!
Ridikkulus!

The slug florishes a nice afro and colorful sunglasses.

Pop! The boggart becomes a hippogriff.

Pres Holding

Riddikulus!
Riddikkulus!

The hippogriff boggart shrank to the size of a caldron and started to nuzzle you.

Pop! The boggart turned into a gigantic spider.

Riddikulus!
Riddikkulus!

The gigantic spider now has roller-skates and is trying to skate.

Pop! The boggart turned into your own death.

To kill someone and then drink their blood is better than drinking someone's blood then killing them

Riddikulus!
The death turns to be a dream which was a visit from professor. A new beginning

Pop! The boggart becomes a pond of blood.

“We are the Pilgrims, master; we shall go always a little further; it may be beyond that last blue mountain barred with snow, across that angry or that glimmering sea." - J.E. Flecker

Riddikulus!
It turns into a pond of lemonade.

Pop! The boggart turns into a horde of slimy (ew) leeches.

viva la vida

Riddikulus!
Pop~ The leaches turn bright pink and start singing (like in google's blob opera)

Pop! The boggart spreads out across the floor off the room, and turns into...well the fear of heights. You find yourself looking down off the edge off a frail rope bridge

Riddikulus!
Riddikulus! The rope bridge turns into a diving board with an enormous pool below it!

Pop! The boggart turns into millions of bandages that begin to encase you like a mummy! :shock2:

"Things are never so bad they can't be made worse." -Elim Garak

Riddikulus!
Riddikulus! The millions of bandages flatten and fold over theirselves becoming paper airplanes that fly around the room

Pop! The Boggart turns into hundreds of scorpions that come crawling toward you at once!

"There's no such thing as strange creatures, only blinked people" - Newt Scamander

Riddikulus!
Riddikulus! The scorpions turns into confettis that pop all around the room!

Pop! The boggart turns into a giant rat that starts to run towards you