Arkham Horror

Whenever you attempt to leave or end movement in an area containing one or more monsters you must either fight or evade each monster; if you fail to evade you take its damage and enter combat, and once you begin combat your movement ends (pp. 6–8, 14).

If a gate opens where an investigator is, that investigator is immediately drawn through to the first area of the Other World and is delayed (place the marker on its side), so they receive no movement points on their next Movement Phase (pp. 9–10, 8).

Closing a gate requires entering and exploring the Other World, returning with an explored marker, then succeeding at a Lore or Fight check to remove the gate marker; sealing a gate is done after a successful close by spending 5 Clue tokens (or using an Elder Sign) to place an elder‑sign token and permanently prevent future gates/monsters at that location (pp. 17–18).

You always make the Horror check (Will) first to see if you lose Sanity, and only afterward choose to flee or fight and resolve the Evade or Combat check (pp. 14–15).

A gate is sealed by spending five Clue tokens after successfully closing it (or by using an Elder Sign); the rule describes the closing player spending the five clues, so sealing is performed when that investigator spends the required Clue tokens or an Elder Sign (pp. 17–18).

There are five awakening triggers (doom track filled by gate openings, too many open gates, no gate markers left, empty monster cup, or terror 10 with too many monsters); placing a doom token on the last doom space immediately awakens the Ancient One and you proceed to the final battle (pp. 10, 20).