- +1 Attrition for enemies
- +25% Improve relations
- −5% Mercenary cost
- +5% Mercenary discipline
- −15% Advisor cost
- +1 Possible advisor
- +20% Domestic trade power
- +2 Tolerance of the true faith
- +20% Fort defense
- +1 Yearly legitimacy
- +0.3 Yearly republican tradition
- +15% National manpower modifier
- +10% Production efficiency
Offaly is a difficult nation to play as, because as soon as England has recovered 60% of its manpower, it will gain claims on all of Ireland. This will usually happen after the initial Surrender of Maine and war with France and after the war of the roses.
Initially there are two different choices. Try to stay in Ireland or try to flee to the new world. If you plan on staying in Ireland, prioritize annexing as many Irish provinces as possible and choice military ideas. If you plan to flee to the new world, take colonization ideas, discover America, and colonize less than five provinces in a colonial region. This is very important, as otherwise, it will form a Colonial Nation.
For the Spanish Fly achievement, forming Ireland or any other tag will prevent the achievement. The easiest way to get it is to take a single province from Spain with another tag's core (e.g. Asturias), release it as a vassal, use the "place dynasty on throne" subject interaction, annex them, return their core via the province button, claim their throne, and declare war with restoration of the Union CB and enforce the union.