Rammus should leverage his high gank threat and mobility to punish overextended lanes rather than trying to match Trundle's clear speed or dueling early.
Focus on cross-map pressure and avoid direct early fights since Trundle has stronger early dueling and invade resistance.
This matchup favors scaling and objective control through ganks and taunt lockdown rather than early jungle skirmishes.
Jungle Plan
Prioritize pathing toward overextended AD-heavy lanes to use (Q) and (E) to lock down key targets early.
Fight for river control and Scuttle only when nearby lanes can move first to avoid getting caught by Trundle's strong dueling.
Use cross-map ganks and counter-jungle camps when Trundle commits to side-lane pressure or extended fights.
Danger windows
Respect Trundle's early invade window where his dueling and sustain are strongest, especially around level 3 to 6.
Avoid isolated river fights where Trundle can trap you with (E) Pillar and force unfavorable skirmishes.
Be cautious when contesting objectives without lane priority, as Trundle's strong objective control and (R) can turn fights against you.
Early game
Start with a three or four-camp clear aimed at lanes that can capitalize on your ganks to maximize early pressure.
Avoid contesting first Scuttle Crab unless your lanes have priority and you can safely counter-gank.
Ward defensively against Trundle's potential early river invades, especially before your armor and taunt value ramp up.
Power spikes
At level 6, use (R) to initiate taunts and knockups on priority targets before Trundle can fully apply his (R) stat drain.
Exploit your anti-AD scaling to outlast Trundle in teamfights, especially against his tanky frontline.
Punish Trundle when his (W) is down, as his healing and movement slow, reducing his dueling threat.
Win conditions
Convert early gank pressure into dragon and Rift Herald control by coordinating with lanes that have priority.
Use your taunt and knockup crowd control to lock down enemy carries in teamfights, negating Trundle's frontline advantage.
Deny Trundle's scaling by counter-jungling when he commits to side-lane splitpushes and force him into unfavorable fights with your mobility and crowd control.
Tip: For Rammus vs Trundle, read overview, trading pattern, and danger windows first for a fast Jungle lane check.