Fantasy Magic around 1990 Main Character Tobias has a sister - Think a blob combines with him to give him powers

[Gavin]

Fantasy Magic around 1990 Main Character Tobias has a sister - Think a blob combines with him to give him powers

[Lobstergirl, au gratin]

Gavin is still looking and wrote:

"I read a book over 20 Years ago
the Main character was tobias - he has a mother and sister also
He visited a lake where he was attacked by a blob creature that gave him powers
He had to battle against an army in the forest."

[Kris]

Gavin, is this book for teens or adults? How old is the main character?

What type of powers?

Location/ country?