Otter

Strategies
The Otter is a sure bet in all early decks, and it's quite useful in mid and even in late decks. It has an above avarage Health and Attack and can tank some of the strongest cards. Although, there are better options in terms of defense and attack, so don't abuse the Otter.

When having Energize, the Otter is one of the best cards to play first at the beggining of the match, granting you the opportunity of playing more cards than your opponent with no risk.

Once you get the Snow Leopard card, there is no need to keep the Otter in your deck unless you combine them both to have a more versatile deck (or an Energize based deck). Unless you have the Otter card at level 10 or above or you need the Revive ability in your strategy, the Snow Leopard is objectively a better option.

Other card that serves exactly the same function as the Otter is the Platypus. It has more damage and the same Health, Deploy Time and Attack Time. The only reason to use the Otter over the Platypus is because their abilities, specially before the Platypus gets Energize. Once the Platypus gets to Level 7, the only reason to pick the Otter before the Platypus is because you want its Revive ability or because its level is higher.