Because its a Stage 2 card, its a little more difficult to set up, but it might have a place in some Psychic decks built around control
It can benefit from a lot of typal benefits that come with its merfolk creature type
When that turns out to not be true, and he's laughed at by people in town, he is filled with rage and takes out his anger on his staff, as shown in many of the cards with "Tyrant" in their name
At worst he is a five mana spot removal one for one that also fogs them for a turn
It might not be as flashy as the usual spellslinging approach the colours are known for, but if you need a Mishras Research Desk or Aeronauts Wings to finish the job, then so be it
Sure, the fact that the Shambler has kicker means it doesnt work well with some Slime tricks, such as flickering or recursion for triggering its ability, but its a 3/3 beater that can destroy a planeswalker