Children's fantasy book or series where a boy and girl are given ink by a squid

Question

A boy and girl go on adventures. One of them involves a merman who becomes a misunderstood monster, maybe, but they turn him back to normal. On this adventure they meet a squid which gives them ink and a blackbird/crow drops the ink on a mean girl's head.

Another adventure involves defeating an evil snow/ice queen who later on, probably in another book becomes an evil sun empress. The girl is from a normal world while the boy is from the fantasy world and works for someone.

Not sure when it was published but it's easy to read with no ye old English. Probably for 10 year olds, I read it about 10 years ago.

Answer 1

As noted by Brian above, this could be the Beast Quest series ghostwritten under the name of Adam Blade. A general overview of the series:

If you, like I, were worried that Adam Blade's Beast Quest would be an extremely black-and-white adventure series about children pointlessly slaughtering Always Chaotic Evil "monsters", you can stop worrying. It's not quite that bad. Rather, it's a series in which two preteens, Tom and Elenna of Avantia, go on a quest to save the mythological Beasts--guardians of Avantia--from the brainwashing powers of Devimon's Black Gears.

There are over a hundred books in the overall series, divided into smaller sets of six books. The squid might be Zepha the Monster Squid from the eponymous seventh book.

One thing that does not match is that both Tom and Elenna are from the fantasy world of the setting.