Sentinels

• Through training and study, a sentinel can enter a trance in which they maintain perfect awareness of their surroundings. They detect minute changes in air currents, vibrations and temperature to detect even the most invisible beings. The trance requires extreme concentration so they can't speak, eat or even have conscious thoughts during the trance.

• Combined with highly trained fighting skills, they can intercept most attacks before they happen.

• They make good bodyguards and sentinals but poor diplomats or conservationists

5e dnd feature - Sentry's Trance

Starting at x level, you can 1 minute to enter a special trance that heightens your senses to detect minute disturbances in air currents, temperature and vibrations in the surrounding environment. This trance lasts 1 hour, but ends early if you take damage or choose to end it (no action required). For the duration of the trance, you can move but cannot speak and are otherwise incapacitated. While in this trance, you cannot be surprised, you have true sight out to 30ft, and you know the location and size of any creatures within 30ft.

explicitly allow observation checks (e.g. perception)

Higher level enhancements

Whenever you are in a trance, and you see a creature within 30ft make an attack or cast a spell, you may use a reaction to end the trance, move up to your full movement towards them and take an opportunity attack against that creature.

While in a trance, you can perform Wisdom (Insight) and Wisdom (Perception) checks with advantage.

Kids on Bikes Strength - Sentry's Trance

When you use a planned action to observe your environment, you gain a +5 to any rolls to do so, provided you do not speak or take other actions for at least a minute prior.