A luminous creature bottle-fed by Newt Scamander inside his case in 1926 New York (WFT).
Commentary
Notes
While not named in the movie script, the glowing tentacled creature is known as a "Marmite" according to the special effects artists at Deluxe's Method Studios:
On the creatures side, Method handled the shot of Newt bottle-feeding a young marmite – a tentacled cross between a dust mite and squid with a transparent body. Production provided live action plates with the actor, and Method artists added the CG creature to the shot, digitally wrapping 10-foot long tentacles around Newt and creating an underwater feel.
"Marmite" is also the name of a sticky brown paste made from yeast leftover from beer brewing. It is bottled and sold as a snack food in Britain and New Zealand, and is similar in taste to Australia's popular Vegemite.
From the Web
Deluxe’s Method Studios Contributes VFX Magic to WB’s “Fantastic Beasts and Where to Find Them”