Just another big creature.
The secret with creatures like Aboroth is that you have to give them something in order for them to be good. For example, if you can give Aboroth flying, or trample, or make it unblockable, then you may have some success with this card. However, that this card slowly withers away is to its detriment. As a high mana cost card, you can’t count on it to still be powerful on the battlefield in a longer, and hard fought game of commander. There is also another problem. Aboroth can be blocked by a 1/1. Sure the 1/1 dies, but several cards would generate a token every turn that could block Aboroth until it was no longer a factor. Thus, this card is essentially worthless unless you can beef it up in some way.