Familiars
Familiars are magical helpers best used for senses, delivery, scouting, and small utility tasks. They are powerful because they give the party another point of view and another position on the map, not because they should dominate the encounter.
Scouting. Familiars can gather information in places the character cannot easily reach, but dangerous areas remain dangerous for small helpers.
Delivery and positioning. Some effects become more flexible when a familiar can occupy a useful space, but timing and range still matter.
Utility identity. A familiar often helps define a caster's style: cautious scout, eerie watcher, trusted assistant, or strange magical extension.
Consequences. If a familiar is exposed to danger, treat that risk clearly. A familiar should be useful, not untouchable by default.
Communication
Be clear about distance, senses, language, and whether the caster is receiving impressions, direct sight, or later behavior from the familiar.
Access
Tiny size and unusual movement are useful, but doors, seals, hostile creatures, weather, and magical wards still create boundaries.
Risk
A familiar that repeatedly enters danger should create meaningful information, meaningful cost, or both.