Creating a creature for character animation by hand is a complex task. In this tutorial I concentrate on the foot only. We build a bone/joint structure for the leg, introduce 3 IK handles and finally group them together.
This is a standard procedure for skeleton management and can be refined, for example to enable a better roll of the foot by using several pivots.
For a basic (and quite popular) tutorial about bones and joints, please see this tutorial: https://youtu.be/PG15ojLPhJY
The music, as always: "Computer Animation" and "dubius 170", composed by me for this channel, licensed via GEMA.